XCB window hoykeys support

XCB window hoykeys support

It kinda suck to have to duplicate this though. Qt4 embedded X video
exhibits the same problem. One ugly "fix" could involve the video
output listening for the parent window event - not sure if this would
work. Another option would be to now create a window in the video
output at all, but then we loose reparenting (useless?). In either
cases, handling of hotkeys in fullscreen mode would seem problematic,
unless we handle fullscreen via the window provider too
(control request?).