main: make "gnome-shell" the default gettext domain

Since libmutter uses dgettext(), we can take over the default domain

https://bugzilla.gnome.org/show_bug.cgi?id=649203

src/main.c

@@ -458,6 +458,7 @@ main (int argc, char **argv)
 
   bindtextdomain (GETTEXT_PACKAGE, LOCALEDIR);
   bind_textdomain_codeset (GETTEXT_PACKAGE, "UTF-8");
+  textdomain (GETTEXT_PACKAGE);
 
   ctx = meta_get_option_context ();
   g_option_context_add_main_entries (ctx, gnome_shell_options, GETTEXT_PACKAGE);