Backport Emacs HEAD's fullscreen mode option

This makes it possible to bypass OS X's fullscreen mode.  The changes
were pulled from Emacs's bzr repository with minimal changes to get
them to work with 24.3

This resolves the issues folks had (e.g. #15448) with the now exclusive use of OS X's fullscreen and makes it possible to get behavior similar to the behavior back when homebrew included a fullscreen patch.

And again, this is stuff coming down the pipe from upstream anyway.  This just pulls in the current configurable behavior from their repo.