Fixed assertion when quickly toggling from fullscreen back to fullscreen:
"Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'backgroundWindows not nil in enterFullScreenTransitionWithOptions:animated:activatingIt:'"

To reproduce this, run testsprite2, press Alt-Enter once, again while it's animating to fullscreen, and then again while it's animating out of fullscreen.
Made sure the window had the correct border when manually being brought back from fullscreen mode.
Fullscreen space naming cleanup to avoid confusion with normal fullscreen mode