Do not align height and width on multiples of 16 in XVideo output. This fixes #1604. If someone thinks that this fix isn't correct, please revert this commit ... and explain why it was wrong :)

Only link avcodec with libavcodec, avformat with libavformat, swscale with libswscale, imgresample with libavcodec (small hack include to fix AC_CHECK_LIB code), postproc with libpostproc.

Some more seperation of the different ffmpeg based modules. They're now completely disjoint except for the common chroma.h and fourcc.h headers.

Img resample based module (functionality untested ... but compilation and loading works). Remove unneeded stuff from swscale.

Add fallback to img_resample based plugin if swscale isn't available on the system. img_resample will be built as a seperate module than avcodec to prevent avcodec from refusing to dlopen if img_resample is unavailable (debian...).

Acked by DBus code maintainers

This module scales with nearest neightboor algorithm ... lower it's capability score so that swscale will be used if available instead.

Simplify scale and chroma conversion code a lot. Remove native croping, padding and 'canvassing' support for transcode. Those will be availble through transcode's vfilter chain in the near future.

Port chain filter to new API. Now supports chaining of chroma conversion and scaling operations. Integration of crop/padding still needs to be done. This might need to be moved in the core.

Split ffmpeg module in avcodec (decoders, encoders, deinterlacing), avformat (demuxers, muxers), swscale (scaling, chroma conversion) and postproc modules.

Do not use knowledge about the FFmpeg version in transcode.

With the mutex patch plus a few fixes.
Signed-off-by: Rémi Denis-Courmont <rdenis@simphalempin.com>