Refresh m4 files from gettext upstream
We switched from using gettext as upstream for gnulib stuff to using gnulib directly, in order to get fresher updates. Now, it seems that some gettext's very own .m4 files have not been updated to gnulib though there has been a stable gettext release with those long time ago. Seems we need to follow both projects, and take updates where ever they first become available.
This ticket is about getting everything to *at least* to the level present in gettext-0.21.1 release.