While each stage has at most a GdkFrameClock, the same GdkFrameClock
instance may drive multiple stages per frame. This means that the
mapping between a GdkFrameClock and a ClutterStage is a 1:M one, not a
1:1.
We should store a list of stages associated to each frame clock
instance, so that we can iterate over it when we need to update the
stages.
This commit fixes redraws of applications using multiple stages,
especially when using clutter-gtk.
Nobody has been compiling Clutter with profiling enabled in a long time.
UProf itself hasn't been updated in 5 years, and it still depends on
deprecated components like dbus-glib, with no port to GDBus in sight.
The profiling code was moderately useful in the past, but these days
it's probably better to profile Cogl than Clutter itself; timing
information can be extracted by the timestamp on each diagnostic message
that is now available by default in the CLUTTER_NOTE macro, and we can
add ad hoc counters where needed.
