Make Ogg music track names configurable

With "OggTrackName" in sw.cfg, so you can for example
set it to "MUSIC/Track??.ogg" for the SW Steam version
"??" is used as a placeholder for the actual track number,
apart from that any path up to 255 chars (relative to the
base SW directory) can be configured.
It defaults to "track??.ogg", like before.
Only play oggtrack when cdaudio_track is set

The old logic tried to play oggtrack even if no cdaudio_track
was set, i.e. it just tried to play "track??.ogg"
That obviously makes no sense, so I moved some code around.
Merge branch 'improve-ogg-music' of git://github.com/DanielGibson/jfsw into DanielGibson
Update submodules containing Daniel Gibson's improvements