Update the embedded copy of the expat XML parser to 2.1.0.  It brings
with it a vareity of bug fixes, both security and behavior.  See
http://www.libexpat.org/ for the list.

NOTE: I already backported the expat hash randomization fix in March.

Fixes issue #14340.
diff --git a/Modules/expat/watcomconfig.h b/Modules/expat/watcomconfig.h
new file mode 100644
index 0000000..2f05e3f
--- /dev/null
+++ b/Modules/expat/watcomconfig.h
@@ -0,0 +1,47 @@
+/* expat_config.h for use with Open Watcom 1.5 and above.  */
+
+#ifndef WATCOMCONFIG_H
+#define WATCOMCONFIG_H
+
+#ifdef __NT__
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#undef WIN32_LEAN_AND_MEAN
+#endif
+
+/* 1234 = LIL_ENDIAN, 4321 = BIGENDIAN */
+#define BYTEORDER 1234
+
+/* Define to 1 if you have the `memmove' function. */
+#define HAVE_MEMMOVE 1
+
+/* Define to 1 if you have the <unistd.h> header file. */
+#define HAVE_UNISTD_H 1
+
+/* Define to the address where bug reports for this package should be sent. */
+#define PACKAGE_BUGREPORT "expat-bugs@mail.libexpat.org"
+
+/* Define to the full name of this package. */
+#define PACKAGE_NAME "expat"
+
+/* Define to the full name and version of this package. */
+#define PACKAGE_STRING "expat 2.0.0"
+
+/* Define to the one symbol short name of this package. */
+#undef PACKAGE_TARNAME
+
+/* Define to the version of this package. */
+#define PACKAGE_VERSION "2.0.0"
+
+/* Define to specify how much context to retain around the current parse
+   point. */
+#define XML_CONTEXT_BYTES 1024
+
+/* Define to make parameter entity parsing functionality available. */
+#define XML_DTD 1
+
+/* Define to make XML Namespaces functionality available. */
+#define XML_NS 1
+
+#endif
+