Replace FFmpeg with Libav in licence headers
Signed-off-by: Mans Rullgard <email@example.com>
Prefix all _demuxer, _muxer, _protocol from libavformat and libavdevice.
This also lists the objects from those two libraries as internal (by addingthe ff_ prefix) so that they can then be hidden via linker scripts.
move null muxer to its own file
Originally committed as revision 24985 to svn://svn.ffmpeg.org/ffmpeg/trunk