Merge mp3 support from Orphis' old FFMPEG code.

Conflicts:
	CMakeLists.txt
	Core/HLE/sceAudio.cpp
	Core/HLE/sceMp3.cpp
	Core/HLE/sceMpeg.cpp
Uncomment some unused stack-corrupting code from sceMp3Decode. Update ffmpeg.
Fix sceMp3 build without USE_FFMPEG
Fix crash in mp3 reading.
Merge pull request #1786 from unknownbrackets/mp3-support

Fix crash in mp3 reading
Get mp3 sample rate and channels from FFMPEG instead of trying to detect ourselves.
VERBOSE a log statement
Merge remote-tracking branch 'origin' into mp3-support

Conflicts:
	Core/HLE/sceAudio.cpp
	Core/HLE/sceMp3.cpp
Allow ELFs to be named PBP, there are a bunch of such homebrew floating around it seems
Merge branch 'mp3-support'