Upgrade to expat 2.2.5.

From `Changes`:

  Release 2.2.5 Tue October 31 2017
        Bug fixes:
              #8  If the parser runs out of memory, make sure its internal
                    state reflects the memory it actually has, not the memory
                    it wanted to have.
             #11  The default handler wasn't being called when it should for
                    a SYSTEM or PUBLIC doctype if an entity declaration handler
                    was registered.
       #137 #138  Fix a case of mistakenly reported parsing success where
                    XML_StopParser was called from an element handler
            #162  Function XML_ErrorString was returning NULL rather than
                    a message for code XML_ERROR_INVALID_ARGUMENT
                    introduced with release 2.2.1

        Other changes:
            #106  xmlwf: Add argument -N adding notation declarations
        #75 #106  Test suite: Resolve expected failure cases where xmlwf
                    output was incomplete
            #127  Windows: Fix test suite compilation
       #126 #127  Windows: Fix compilation for Visual Studio 2012
        #33 #132  tests: Mass-fix compilation for XML_UNICODE_WCHAR_T
            #129  examples: Fix compilation for XML_UNICODE_WCHAR_T
            #130  benchmark: Fix compilation for XML_UNICODE_WCHAR_T
            #144  xmlwf: Fix compilation for XML_UNICODE_WCHAR_T; still needs
                    Windows or MinGW for 2-byte wchar_t
              #9  Address two Clang Static Analyzer false positives
             #59  Resolve troublesome macros hiding parser struct membership
                    and dereferencing that pointer
              #6  Resolve superfluous internal malloc/realloc switch
       #153 #155  Improve docbook2x-man detection
            #160  Undefine NDEBUG in the test suite (rather than rejecting it)
            #161  Address compiler warnings
                  Version info bumped from 7:6:6 to 7:7:6

        Special thanks to:
            Benbuck Nason
            Hans Wennborg
            José Gutiérrez de la Concha
            Pedro Monreal Gonzalez
            Rhodri James
            Rolf Ade
            Stephen Groat
                 and
            Core Infrastructure Initiative

  Release 2.2.4 Sat August 19 2017
        Bug fixes:
            #115  Fix copying of partial characters for UTF-8 input

        Other changes:
            #109  Fix "make check" for non-x86 architectures that default
                    to unsigned type char (-128..127 rather than 0..255)
            #109  coverage.sh: Cover -funsigned-char
                  Autotools: Introduce --without-xmlwf argument
             #65  Autotools: Replace handwritten Makefile with GNU Automake
             #43  CMake: Auto-detect high quality entropy extractors, add new
                    option USE_libbsd=ON to use arc4random_buf of libbsd
             #74  CMake: Add -fno-strict-aliasing only where supported
            #114  CMake: Always honor manually set BUILD_* options
            #114  CMake: Compile man page if docbook2x-man is available, only
            #117  Include file tests/xmltest.log.expected in source tarball
                    (required for "make run-xmltest")
            #117  Include (existing) Visual Studio 2013 files in source tarball
                  Improve test suite error output
            #111  Fix some typos in documentation
                  Version info bumped from 7:5:6 to 7:6:6

        Special thanks to:
            Jakub Wilk
            Joe Orton
            Lin Tian
            Rolf Eike Beer

  Release 2.2.3 Wed August 2 2017
        Security fixes:
             #82  CVE-2017-11742 -- Windows: Fix DLL hijacking vulnerability
                    using Steve Holme's LoadLibrary wrapper for/of cURL

        Bug fixes:
             #85  Fix a dangling pointer issue related to realloc

        Other changes:
                  Increase code coverage
             #91  Linux: Allow getrandom to fail if nonblocking pool has not
                    yet been initialized and read /dev/urandom then, instead.
                    This is in line with what recent Python does.
             #81  Pre-10.7/Lion macOS: Support entropy from arc4random
             #86  Check that a UTF-16 encoding in an XML declaration has the
                    right endianness
        #4 #5 #7  Recover correctly when some reallocations fail
                  Repair "./configure && make" for systems without any
                    provider of high quality entropy
                    and try reading /dev/urandom on those
                  Ensure that user-defined character encodings have converter
                    functions when they are needed
                  Fix mis-leading description of argument -c in xmlwf.1
                  Rely on macro HAVE_ARC4RANDOM_BUF (rather than __CloudABI__)
                    for CloudABI
            #100  Fix use of SIPHASH_MAIN in siphash.h
             #23  Test suite: Fix memory leaks
                  Version info bumped from 7:4:6 to 7:5:6

        Special thanks to:
            Chanho Park
            Joe Orton
            Pascal Cuoq
            Rhodri James
            Simon McVittie
            Vadim Zeitlin
            Viktor Szakats
                 and
            Core Infrastructure Initiative

  Release 2.2.2 Wed July 12 2017
        Security fixes:
             #43  Protect against compilation without any source of high
                    quality entropy enabled, e.g. with CMake build system;
                    commit ff0207e6076e9828e536b8d9cd45c9c92069b895
             #60  Windows with _UNICODE:
                    Unintended use of LoadLibraryW with a non-wide string
                    resulted in failure to load advapi32.dll and degradation
                    in quality of used entropy when compiled with _UNICODE for
                    Windows; you can launch existing binaries with
                    EXPAT_ENTROPY_DEBUG=1 in the environment to inspect the
                    quality of entropy used during runtime; commits
                    * 95b95032f907ef1cd17ee7a9a1768010a825d61d
                    * 73a5a2e9c081f49f2d775cf7ced864158b68dc80
   [MOX-006]      Fix non-NULL parser parameter validation in XML_Parse;
                    resulted in NULL dereference, previously;
                    commit ac256dafdffc9622ab0dc2c62fcecb0dfcfa71fe

        Bug fixes:
             #69  Fix improper use of unsigned long long integer literals

        Other changes:
             #73  Start requiring a C99 compiler
             #49  Fix "==" Bashism in configure script
             #50  Fix too eager getrandom detection for Debian GNU/kFreeBSD
             #52    and macOS
             #51  Address lack of stdint.h in Visual Studio 2003 to 2008
             #58  Address compile warnings
             #68  Fix "./buildconf.sh && ./configure" for some versions
                    of Dash for /bin/sh
             #72  CMake: Ease use of Expat in context of a parent project
                    with multiple CMakeLists.txt files
             #72  CMake: Resolve mistaken executable permissions
             #76  Address compile warning with -DNDEBUG (not recommended!)
             #77  Address compile warning about macro redefinition

        Special thanks to:
            Alexander Bluhm
            Ben Boeckel
            Cătălin Răceanu
            Kerin Millar
            László Böszörményi
            S. P. Zeidler
            Segev Finer
            Václav Slavík
            Victor Stinner
            Viktor Szakats
                 and
            Radically Open Security

  Release 2.2.1 Sat June 17 2017
        Security fixes:
                  CVE-2017-9233 -- External entity infinite loop DoS
                    Details: https://libexpat.github.io/doc/cve-2017-9233/
                    Commit c4bf96bb51dd2a1b0e185374362ee136fe2c9d7f
   [MOX-002]      CVE-2016-9063 -- Detect integer overflow; commit
                    d4f735b88d9932bd5039df2335eefdd0723dbe20
                    (Fixed version of existing downstream patches!)
   (SF.net) #539  Fix regression from fix to CVE-2016-0718 cutting off
                    longer tag names; commits
                    * 896b6c1fd3b842f377d1b62135dccf0a579cf65d
                    * af507cef2c93cb8d40062a0abe43a4f4e9158fb2
             #16    * 0dbbf43fdb20f593ddf4fa1ff67288000dd4a7fd
             #25  More integer overflow detection (function poolGrow); commits
                    * 810b74e4703dcfdd8f404e3cb177d44684775143
                    * 44178553f3539ce69d34abee77a05e879a7982ac
   [MOX-002]      Detect overflow from len=INT_MAX call to XML_Parse; commits
                    * 4be2cb5afcc018d996f34bbbce6374b7befad47f
                    * 7e5b71b748491b6e459e5c9a1d090820f94544d8
   [MOX-005] #30  Use high quality entropy for hash initialization:
                    * arc4random_buf on BSD, systems with libbsd
                      (when configured with --with-libbsd), CloudABI
                    * RtlGenRandom on Windows XP / Server 2003 and later
                    * getrandom on Linux 3.17+
                    In a way, that's still part of CVE-2016-5300.
                    https://github.com/libexpat/libexpat/pull/30/commits
   [MOX-005]      For the low quality entropy extraction fallback code,
                    the parser instance address can no longer leak, commit
                    04ad658bd3079dd15cb60fc67087900f0ff4b083
   [MOX-003]      Prevent use of uninitialised variable; commit
   [MOX-004]        a4dc944f37b664a3ca7199c624a98ee37babdb4b
                  Add missing parameter validation to public API functions
                    and dedicated error code XML_ERROR_INVALID_ARGUMENT:
   [MOX-006]        * NULL checks; commits
                      * d37f74b2b7149a3a95a680c4c4cd2a451a51d60a (merge/many)
                      * 9ed727064b675b7180c98cb3d4f75efba6966681
                      * 6a747c837c50114dfa413994e07c0ba477be4534
                    * Negative length (XML_Parse); commit
   [MOX-002]          70db8d2538a10f4c022655d6895e4c3e78692e7f
   [MOX-001] #35  Change hash algorithm to William Ahern's version of SipHash
                    to go further with fixing CVE-2012-0876.
                    https://github.com/libexpat/libexpat/pull/39/commits

        Bug fixes:
             #32  Fix sharing of hash salt across parsers;
                    relevant where XML_ExternalEntityParserCreate is called
                    prior to XML_Parse, in particular (e.g. FBReader)
             #28  xmlwf: Auto-disable use of memory-mapping (and parsing
                    as a single chunk) for files larger than ~1 GB (2^30 bytes)
                    rather than failing with error "out of memory"
              #3  Fix double free after malloc failure in DTD code; commit
                    7ae9c3d3af433cd4defe95234eae7dc8ed15637f
             #17  Fix memory leak on parser error for unbound XML attribute
                    prefix with new namespaces defined in the same tag;
                    found by Google's OSS-Fuzz; commits
                    * 16f87daae5a16132e479e4f71862128c7a915c73
                    * b47dbc9745932c160893d433220e462bd605f8cd
                  xmlwf on Windows: Add missing calls to CloseHandle

        New features:
             #30  Introduced environment switch EXPAT_ENTROPY_DEBUG=1
                    for runtime debugging of entropy extraction

        Other changes:
                  Increase code coverage
             #33  Reject use of XML_UNICODE_WCHAR_T with sizeof(wchar_t) != 2;
                    XML_UNICODE_WCHAR_T was never meant to be used outside
                    of Windows; 4-byte wchar_t is common on Linux
   (SF.net) #538  Start using -fno-strict-aliasing
   (SF.net) #540  Support compilation against cloudlibc of CloudABI
                  Allow MinGW cross-compilation
   (SF.net) #534  CMake: Introduce option "BUILD_doc" (enabled by default)
                    to bypass compilation of the xmlwf.1 man page
   (SF.net)  pr2  CMake: Introduce option "INSTALL" (enabled by default)
                    to bypass installation of expat files
                  CMake: Fix ninja support
                  Autotools: Add parameters --enable-xml-context [COUNT]
                    and --disable-xml-context; default of context of 1024
                    bytes enabled unchanged
             #14  Drop AmigaOS 4.x code and includes
             #14  Drop ancient build systems:
                    * Borland C++ Builder
                    * OpenVMS
                    * Open Watcom
                    * Visual Studio 6.0
                    * Pre-X Mac OS (MPW Makefile)
                    If you happen to rely on some of these, please get in
                    touch for joining with maintenance.
             #10  Move from WIN32 to _WIN32
             #13  Fix "make run-xmltest" order instability
                  Address compile warnings
                  Bump version info from 7:2:6 to 7:3:6
                  Add AUTHORS file

        Infrastructure:
              #1  Migrate from SourceForge to GitHub (except downloads):
                    https://github.com/libexpat/
              #1  Re-create http://libexpat.org/ project website
                  Start utilizing Travis CI

        Special thanks to:
            Andy Wang
            Don Lewis
            Ed Schouten
            Karl Waclawek
            Pascal Cuoq
            Rhodri James
            Sergei Nikulov
            Tobias Taschner
            Viktor Szakats
                 and
            Core Infrastructure Initiative
            Mozilla Foundation (MOSS Track 3: Secure Open Source)
            Radically Open Security

Bug: N/A
Test: cts-tradefed run cts -m CtsLibcoreTestCases -t libcore.xml.ExpatSaxParserTest
Change-Id: Ide6a7b30ed05cbd712cc88350381e9dbbc5d79ad
diff --git a/conftools/expat.m4 b/conftools/expat.m4
new file mode 100644
index 0000000..57e579b
--- /dev/null
+++ b/conftools/expat.m4
@@ -0,0 +1,43 @@
+dnl Check if --with-expat[=PREFIX] is specified and
+dnl Expat >= 1.95.0 is installed in the system.
+dnl If yes, substitute EXPAT_CFLAGS, EXPAT_LIBS with regard to
+dnl the specified PREFIX and set with_expat to PREFIX, or 'yes' if PREFIX
+dnl has not been specified. Also HAVE_LIBEXPAT, HAVE_EXPAT_H are defined.
+dnl If --with-expat has not been specified, set with_expat to 'no'.
+dnl In addition, an Automake conditional EXPAT_INSTALLED is set accordingly.
+dnl This is necessary to adapt a whole lot of packages that have expat
+dnl bundled as a static library.
+AC_DEFUN([AM_WITH_EXPAT],
+[ AC_ARG_WITH(expat,
+	      [  --with-expat=PREFIX     Use system Expat library],
+	      , with_expat=no)
+
+  AM_CONDITIONAL(EXPAT_INSTALLED, test $with_expat != no)
+
+  EXPAT_CFLAGS=
+  EXPAT_LIBS=
+  if test $with_expat != no; then
+	if test $with_expat != yes; then
+		EXPAT_CFLAGS="-I$with_expat/include"
+		EXPAT_LIBS="-L$with_expat/lib"
+	fi
+	AC_CHECK_LIB(expat, XML_ParserCreate,
+		     [ EXPAT_LIBS="$EXPAT_LIBS -lexpat"
+		       expat_found=yes ],
+		     [ expat_found=no ],
+		     "$EXPAT_LIBS")
+	if test $expat_found = no; then
+		AC_MSG_ERROR([Could not find the Expat library])
+	fi
+	expat_save_CFLAGS="$CFLAGS"
+	CFLAGS="$CFLAGS $EXPAT_CFLAGS"
+	AC_CHECK_HEADERS(expat.h, , expat_found=no)
+	if test $expat_found = no; then
+		AC_MSG_ERROR([Could not find expat.h])
+	fi
+	CFLAGS="$expat_save_CFLAGS"
+  fi
+
+  AC_SUBST(EXPAT_CFLAGS)
+  AC_SUBST(EXPAT_LIBS)
+])