Don't add 'gnulib-lib' to include path when compiling libgettextpo tests.
po-gram: fix memory leaks
libintl: Fix pointer use after free and make error handling robuster

Previously, _nl_find_msg had a use of pointer after free'd.  Also,
some callers of the function didn't check the failure.

Merge changes from glibc.  Reported by Carlos O'Donell in
<https://savannah.gnu.org/bugs/?38930>.
NEWS: Mention memory leak fix in libgettextpo
autopoint: recognize multiple arguments of AM_GNU_GETTEXT when tracing
autopoint: discard stderr of autom4te
msgfmt: adjust the default value of PO-Revision-Date to xgettext
autopoint: use 'm4' as the fallback macro directory
Clear error_message_count before parsing PO files.