Commit c7a1cf3c removes the usage of
AM_GLIB_GNU_GETTEXT, but a variable set by it, DATADIRNAME, is used in
libgnome-desktop/Makefile.am to specify the path to locale data, which
causes bindtextdomain to be called with a wrong path so all translations
are ignored. To fix it, we simply set GNOMELOCALEDIR to localedir.