Karaoke: Smooth out the display while seeking
Karaoke: Report file-read failures more tidily
Karaoke: Add a "Silence all" button in case of stuck notes
Karaoke: Reset channel names and patch names on track switch
Karaoke: Show more lyrics ahead of current position and less behind
Karaoke: No need for line wrap now that lyric lines are shortened forcefully
PlayMIDI/Karaoke: Cope better with broken files
Karaoke: Handle even more weird forms of MIDI lyric elements
Karaoke: Implement playlists.

It looks like a huge edit, but it's actually a straight-forward bolt-on that
changes the playmidis() thread only - nothing else has to change, other than
trivialities. Playlists from vanBasco's Karaoke Player can be read, and a
directory can be recursed into.
Karaoke: Terminate on window close
Karaoke: Allow the user to double-click a playlist entry to jump to it