Fix a couple of missing LIBTHREAD link failures on AIX.

[Ralf Wildenhues]

AIX 5.3 needs -lpthread for git-merge-changelog (through fstrcmp),
and strsignal-tests due to strsignal.  The patch below fixes these.

Thanks,
Ralf

    Fix a couple of missing LIBTHREAD link failures on AIX.
    
    * modules/git-merge-changelog (git_merge_changelog_LDADD): Add
    $(LIBTHREAD).
    * modules/strsignal-tests (test_strsignal_LDADD): Likewise.

diff --git a/modules/git-merge-changelog b/modules/git-merge-changelog
index 94d584e..d0e2ad0 100644
--- a/modules/git-merge-changelog
+++ b/modules/git-merge-changelog
@@ -28,7 +28,7 @@ configure.ac:
 
 Makefile.am:
 bin_PROGRAMS = git-merge-changelog
-git_merge_changelog_LDADD = libgnu.a @LIBINTL@
+git_merge_changelog_LDADD = libgnu.a @LIBINTL@ $(LIBTHREAD)
 
 Include:
 
diff --git a/modules/strsignal-tests b/modules/strsignal-tests
index e845ba5..ab67eb1 100644
--- a/modules/strsignal-tests
+++ b/modules/strsignal-tests
@@ -10,4 +10,4 @@ configure.ac:
 Makefile.am:
 TESTS += test-strsignal
 check_PROGRAMS += test-strsignal
-test_strsignal_LDADD = $(LDADD) @LIBINTL@
+test_strsignal_LDADD = $(LDADD) @LIBINTL@ $(LIBTHREAD)