mpegvideo: remove useless references to h264 and svq3

The h264 decoder does not use mpegvideo anymore. The svq3 decoder only
uses ff_draw_horiz_band().
Merge commit '19cac8e301419dcde31526d15196a952ddf2c4c7'

* commit '19cac8e301419dcde31526d15196a952ddf2c4c7':
  mpegvideo: remove useless references to h264 and svq3

Conflicts:
	libavcodec/mpegvideo.c

Merged-by: Michael Niedermayer <michaelni@gmx.at>
avframe: Copy buffer type in copy_props.

Fixes VDPAU decoding with MPlayer.