Use signals instead of onscreen framebuffer frame callbacks

CoglFrameInfo is a frame info container associated with a single
onscreen framebuffer. The clutter stage will eventually support drawing
a stage frame with multiple onscreen framebuffers, thus needs its own
frame info container.

This patch introduces a new stage signal 'presented' and a accompaning
ClutterFrameInfo and adapts the stage windows and past onscreen frame
callbacks users to use the signal and new info container.

https://bugzilla.gnome.org/show_bug.cgi?id=768976

src/compositor/compositor-private.h

@@ -29,7 +29,6 @@ struct _MetaCompositor
   GList                 *windows;
   Window                 output;
 
-  CoglFrameClosure      *frame_closure;
   CoglContext           *context;
 
   /* Used for unredirecting fullscreen windows */