[spmc] backport bump ffmpeg to 2.3.1

Conflicts:
	lib/ffmpeg/libavcodec/avcodec.h
	lib/ffmpeg/libavcodec/h264.c
	lib/ffmpeg/libavcodec/h264.h
	tools/depends/target/Makefile
	xbmc/cores/dvdplayer/DVDCodecs/Video/libstagefrightRK/StageFrightVideoPrivate.h
Introduce SWCodec - these are codecs that don't have any GPU acceleration (yet) - add HVEC
SWCodec: Add VP9 as pure sw decoder to use multithreading
CHG: Refactor ffmpeg MT support
fixup ffmpeg MT: add iOS
Revert and fix: "AESink: Reset GetLatency() back to match upstream"

* My logic was incorrect. Need to delay latency for both usecases (m_passthrough/!m_passthrough)

Signed-off-by: Brandon McAnsh <brandonm@matricom.net>
Revert "AML: Move/rename ModeToResolution() into AMLUtils as aml_mode_to_resolution()"

This reverts commit f14b19a8fc4efae7cfe4448d33594d143856c9ba.
Introduce Amlogic M8 4K video format on Android 4.4
[libamplayer] Add HEVC format to Android 4.4 patch
xbmc: add amcodec target

* Build amcodec dependencies

Signed-off-by: Brandon McAnsh <brandonm@matricom.net>