This limits ABI issues in case libavcodec is linked to a libavutil with larger AVFrame
Which can happen if they are shiped in seperate binary packages and libavutil is upgraded

A cleaner alternative would be to replace them by pointers but this would likely cause
a small speedloss
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit fc567ac4)

Conflicts:

	libavcodec/h264.h
(cherry picked from commit 618d062bd553a7d7fad194d4236913f2b0a0251e)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>