Fixes and tweaks for OpenSL.
(frontend.c) Only cater to new OSX port/iOS for now
Use GCC atomics to avoid locking in callback.
(APPLE) Build fixes for new frontend.c
(APPLE) Take out SDL/GL context parts for OSX
Use 44.1kHz audio on Android.

Should be toggleable (or use autodetect if present on Android 4.2+).
Fixes audio on Nexus 10 in my test case.
Check for hardware sampling rate automatically.
Merge branch 'master' of github.com:libretro/RetroArch into opensl

Conflicts:
	frontend/frontend.c
Purge SDL/GL context.