pixman_region32_t is an efficient well tested region implementation (its
the one used in X) that we already depend on via pixman and use in
some places. No need to have a custom region implementation.
-move _focused & _pointer_in_window from RedWindow to RedWindow_p's
-move shadow focus & cursor handling to sync()
-add reset_cursor_pos() to Platform
-Monitor set_mode()/restore() use virtual do_set_mode()/do_restore()
Additional changes that were required for the feature:
1) focusing on the pointed window in full screen mode
2) In X11 - handling events that occur during keyboard ungrabbing
3) In X11 - handling Leave/Enter Notify events that occur during keyboard grabbing/ungrabbing
4) In X11 - fix for focus events that are handled in the wrong order (happens when
focus events occur during grabbing the keyboard)
5) In X11 - ignoring key release events during key holding
6) In Windows - synchronizing keyboard release events that occured during a modal loop
