Fix compile problem.
Fix messed demuxer.
Merge branch 'develop' into libav
Split plugin Libav from FFmpeg.
Merge branch 'develop' into libav

Conflicts:
	plugins/ffmpeg/CMakeLists.txt
Update cmake scripts.
Merge branch 'develop' into libav
Split CMake module from FFmpeg.
Fix compile problem.
Rename files.
Add option to switch between Libav and FFmpeg.