macosx: implement vout actions handling for multiple vout windows

macosx: implement vout actions handling for multiple vout windows

Now, everything from the video menu and the basic stuff like fullscreen
should work. If it does'nt (e.g. fullscreen and resize with video-splitter module enabled)
please blame the core first. ;-)

TODO: There might be some getVout()-calls left which should be investigated.

close #6814