Merge commit '7d848264'

* commit '7d848264':
  cavs: deMpegEncContextize

Note, the bugfixes have all been in FFmpeg previously, this just switches away
from MpegEncContext

Conflicts:
	libavcodec/cavs.c
	libavcodec/cavsdec.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>