* clutter/clutter-actor.c:
(clutter_actor_set_parent): Document and maintain the invariant
that after setting a realized parent on an actor, the actor is
also going to be realized.
(clutter_actor_unparent): Change the invariant that an unparented
actor is also unrealized: the paint is fast enough to avoid
unrealizing, since it also causes more problems that what it's
worth.
* tests/test-invariants.c (test_show_on_set_parent): Update the
invariants test because we changed the invariants.
* clutter/clutter-actor.c (clutter_actor_unparent): Reset the
:show-on-set-parent property to TRUE when unparenting.
* tests/Makefile.am: Add test-invariant to the build.
* tests/test-invariants.c: Test the invariants that we are going
to honour (and document, at some point).
