clutter/actor: Allow setting width and height properties to -1.0
ClutterActors width and height can be reset to automatically use the
preferred (calculated) value by setting the width or height to -1, so
far this only works by setting it using clutter_actor_set_width()
or
clutter_actor_set_height()
, make sure it can also be done using the
"width" and "height" GObject properties.