mpegvideo: directly use frames in ff_draw_horiz_band()
h264: directly use frames in ff_h264_draw_horiz_band()
er: move relevant fields from Picture to ERPicture

This is done to disentangle ER from mpegvideo. In order to use a
classic Picture, callers can use ff_mpeg_set_erpic() or use a custom function
to set the fields. Please note that buffers need to be allocated before
calling ff_er_frame_end().
h264: move relevant fields from Picture to H264Picture
h264: Replace mpegvideo-specific MAX_PICTURE_COUNT by private define
h264: Replace mpegvideo-specific MAX_THREADS by private define
h264: Remove MotionEstContext and move the relevant fields to H264Context

Unused buffers scratchpad and temp have been dropped too.
mpegvideo: move mpegvideo formats-related defines to mpegutils.h
mpegvideo: move ff_draw_horiz_band() to mpegutils.c

Drop the mpegvideo dependency for svq3 in configure.
mpegvideo: remove h264-only fields
h264 does not depend on mpegvideo any more
RGBA64 pixel formats

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
isom: fix C99-style declaration
codec_desc: update dvaudio tag