Bug 1380 - Return booleans from CLUTTER_ACTOR_IS_* macros

Bug 1380 - Return booleans from CLUTTER_ACTOR_IS_* macros

If you try to use the CLUTTER_ACTOR_IS_* macros defined in ClutterActor
like this:

  typedef struct { unsigned int reactive : 1; } foo_t;

  foo_t f; f.reactive = CLUTTER_ACTOR_IS_REACTIVE (actor);

It will blow up because while the macros evaluate to 0 they can also
evaluate to non-zero values. Since most of the boolean flags in
Clutter and Clutter-based code are going to be stored like in the
example above, we should change the macros and let them evaluate
stricly either to 0 or to 1.