Mac OS X gui: checkForUpdate may not run on first thread. Hence alloc an autorelease pool in checkForUpdate.

	       * improve readability of macros	 

- getaddrinfo.c : cleanup replacement APIs for win32 and make sure the shim logic only searches for real APIs only once

- control/input.c: don't rely on exceptions to control the state of API internal logic as these are optional

Enable ffmpeg's GIF decoder for post r8520 revisions (Many thanks to Baptiste Coudurier for fixing the bug(s)).

Gestures: Fix two dead locks when changing audio track and subtitle track when there is no such track.