vf_frei0r: adjust error messages
vf_frei0r: prevent a segfault when filter parameters are not set
vf_frei0r: refactor library loading from env variable

strtok_r is not needed any more, so remove it from configure.
mathops: move macro to the only place it is used

This helps in disentangling lavf and lavc too.
put_bits: Remove unused includes

This requires adding includes to other files that relied on these being
included implicitly.
mpegvideo: directly use frames in ff_draw_horiz_band()
er: move relevant fields from Picture to ERPicture

A new function is introduced to keep compatibility across the code.
h264: move relevant fields from Picture to H264Picture

A new function is introduced to support ERPicture.
h264: directly use frames in ff_h264_draw_horiz_band()
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 in H264Context
mpegvideo: move PICT_* macros into picttype.h

Also adjust the headers as needed.
mpegvideo: move MB_TYPE_* and IS_* macros to mbtype.h

Also adjust the headers as needed.
mpegvideo: move ff_draw_horiz_band() in utils.c
mpegvideo: remove h264-only fields
h264 does not depend on mpegvideo anymore
WIP: h264 with no struct avframe
svq3: use AVFrame API properly
h264: use AVFrame API properly