When using the new ActorAlign flags we must get the real alignment for
the horizontal axis, as clutter_actor_allocate() will compute the
effective alignment by itself; if we use the effective alignment then
ClutterActor.allocate() will swap it, and undo our work.
When using the old BinAlignment flags we should reverse the alignment
depending on whether the text direction of the child is RTL or LTR.
See bug: https://bugzilla.gnome.org/show_bug.cgi?id=684214
