libdw: Add support for DWZ multifile forms DW_FORM_GNU_ref_alt/strp_alt.

DWZ multifile forms http://www.dwarfstd.org/ShowIssue.php?issue=120604.1
DW_FORM_GNU_ref_alt and DW_FORM_GNU_strp_alt reference an alternative
debuginfo file.  dwarf_begin and dwarf_begin_elf will try to use this
automatically.  There are no user visible changes to the libdw interface.

dwarf_formref_die, dwarf_formstring and dwarf_formudata can now return
a Dwarf_Die which comes from a CU in the alternative Dwarf descriptor.

__libdw_read_offset was adjusted to take an alternative Dwarf descriptor
into account.

Signed-off-by: Mark Wielaard <mjw@redhat.com>
diff --git a/tests/ChangeLog b/tests/ChangeLog
index 2291b62..1cdd464 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,14 @@
+2012-06-27  Mark Wielaard  <mjw@redhat.com>
+
+	* Makefile.am (TESTS): Add run-readelf-dwz-multi.sh.
+	(EXTRA_DIST): Add run-readelf-dwz-multi.sh,
+	libtestfile_multi_shared.so.bz2, testfile_multi.dwz.bz2 and
+	testfile_multi_main.bz2.
+	* run-readelf-dwz-multi.sh: New test.
+	* libtestfile_multi_shared.so.bz2: New testfile.
+	* testfile_multi.dwz.bz2: New testifle.
+	* testfile_multi_main.bz2: New testifle.
+
 2012-08-01  Petr Machata  <pmachata@redhat.com>
 
 	* run-test-archive64.sh: New test.