Fix bug: gettextize does not add intlmacosx.m4 file.
Reported by Eli Zaretskii via Gavin Smith in
<http://lists.gnu.org/archive/html/bug-texinfo/2017-07/msg00026.html>.
* gettext-tools/misc/gettextize.in (m4filelist): Include intlmacosx.m4 also
when --intl option is not given.
* gettext-tools/doc/gettext.texi (aclocal): Add intlmacosx.m4 to file list.
