[depends] move ffmpeg to unified deps
[configure] remove internal ffmpeg
remove ffmpeg from tree
ffmpeg: remove dll wrappers

Conflicts:
	lib/DllAvCodec.h
	lib/DllAvFormat.h
	xbmc/cores/dvdplayer/DVDCodecs/Video/VAAPI.cpp
	xbmc/cores/dvdplayer/DVDDemuxers/DVDDemuxFFmpeg.cpp
add ffmpeg lock manager
todo: refactor to own file
ffmpeg: move callbacks into separate file
sq to configure - we still need the optimizations switch
squash to drop wrapper
use fmpeg master branch because 2.1 ist broken
Introduce SWCodec - these are codecs that don't have any GPU acceleration (yet) - add HVEC