* clutter/clutter-backend.c: Add more debug messages
* clutter/clutter-stage.h:
* clutter/clutter-stage.c:
(clutter_stage_is_default): Add a function to check if the
stage is the default one.
* clutter/glx/clutter-backend-glx.c:
* clutter/glx/clutter-stage-glx.c:
* clutter/x11/clutter-stage-x11.c: Keep the stage wrapper
and implementation flags in sync, to ensure that the GL
context is always set.