Revert "Use upstream gettext instead the glib one"

This causes several problems:
- Compilation in FreeBSD with --enable-gtk-doc broke
- Modules that still use the AM_GLIB_GNU_GETTEXT macro
  doesnt compile anymore because /usr/share/glib-2.0/gettext
  is not filled with the correct files, as this was done in
  the glib custom po/Makefile.in.in

See https://bugzilla.gnome.org/show_bug.cgi?id=622991

This reverts commit e5c752371c.

Makefile.am

@@ -34,7 +34,6 @@ EXTRA_DIST += 			\
 	ChangeLog.pre-2-2	\
 	ChangeLog.pre-2-0	\
 	ChangeLog.pre-1-2	\
-	config.rpath		\
 	glib-zip.in		\
 	NEWS.pre-1-3		\
 	acglib.m4		\