Limit source code to 80 chars, and declare functions return type and
modifiers on a separate line.
This allows to avoid very long lines, and all function names are
aligned.
(We do this on VLC, and I like it.)
Implement recording to Matroska files.
The format to use is determined by the option -F/--record-format if set,
or by the file extension (".mp4" or ".mkv").
