extractor: More NULL checks...

This is blowing up if media unrecognized by ffmpeg goes through

Change-Id: Idfb2dcf581e3195f05772d375d315a6aedeab993
extractor: Underp mpeg4 fastpath

Only run this _after_ validating the result of avformat_open_input()

Change-Id: Ib7969a7f723ba58219476ceb541e8dd24c7c922b
Don't use ffdshow to downmix the audio stream

send multichannel PCM over supported sound output (HDMI)
if no multichannel output is found the android mixer will downmix

Change-Id: Icea5a89e7669f90a0d7266eeec9eddb20723f6ca
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_external_stagefright-plugins into HEAD