Added -windowDidChangeScreen: delegate to handle condition where movi…

…ng host window to a different screen would cause pick errors to be output. The delegate just causes the stage to be redrawn which re-creates the pick buffer

clutter/osx/clutter-stage-osx.c

@@ -132,6 +132,11 @@ clutter_stage_osx_get_wrapper (ClutterStageWindow *stage_window);
   else 
     return [self frame].size;
 }
+
+- (void)windowDidChangeScreen:(NSNotification *)notification
+{
+  clutter_redraw(CLUTTER_STAGE(self->stage_osx->wrapper));
+}
 @end
 
 /*************************************************************************/