remove custom code
update ffmpeg (n0.8-19651-g36099df)

Notes: broken atm because our custom files need to be updated too

* libavcodec/h264_dxva.c
* libavcodec/h264_recov.c
* libavcodec/vc1_dxva.c
update CFLAGS and ffmpeg/config.asm and ffmpeg/config.h
Fix compilation (not really tested).
n0.8-19666-g98c4268