Cocoa Port:
- Fix bug where video filters weren't preferring to use the GPU by default.
- Display threads now each pull a copy of the video frame from the emulation thread, rather than the emulation thread pushing copies of the video frame to each display thread. (Slight performance improvement when many display threads are used.)

git-svn-id: https://svn.code.sf.net/p/desmume/code/trunk@5034 5577840e-afb3-4e59-9ef3-2b7f898b1952