RTL locales need to translate the "default:LTR" string to have
clutter_actor_get_text_direction() return the expected result;
as GNOME Shell now makes use of that API, users of RTL locales
would be up for an unpleasant surprise, so add all locales that
translate "default:LTR" to "default:RTL" in GTK+.
https://bugzilla.gnome.org/show_bug.cgi?id=671736
