Most part of this commit fixes issues with FFmpeg output with
currently supported codecs:
- avcodec_encode_video might return zero which doesn't mean error
happened, but blender will handle this as error and will stop
rendering to video file.
- Changing output video codec wouldn't update "expert" options
set for video output which leads to some sideeffects like
ignored Lossless option for x264 codec.
This fixes allowed to add QTRLE codec easily.
dc72e79274