[Development] old-style, consistent fullscreen behaviour on Mac

[René J.V. Bertin]

Re: inconsistencies: I just checked video playback in Safari. HTML5 video uses the "native" fullscreen but Flash videos go fullscreen without affecting other screens. I've noticed the same in other browsers, but not in Google Chrome which uses "single-screen fullscreen" regardless the type of video being played. I think that's preferable...

R.