ffmpeg: trim libffmpeg-mini

Minidlna has no need to mux streams, or be able to read network streams at this point in time.

Signed-off-by: Ian Leonard <antonlacon@gmail.com>
ffmpeg: add audio-dec profile to libffmpeg-custom

Signed-off-by: Ian Leonard <antonlacon@gmail.com>
ffmpeg: add external libraries section to Config.in

Signed-off-by: Ian Leonard <antonlacon@gmail.com>