xmms midi file plugin: List of things to do

* Check any remaining references to x11amp.

* Use timidity+, rather than timidity.

* Much bug fixing in the configuration mixer dialog.

* Better displays for VU meters and note indicators in the mixer dialog.

* Do muting (use the same mechanism for solo).

* Do solo'ing in mix.c rather than by not playing notes.

* Provide pan, reverb, etc controls.

* Provide a method of saving volume settings back into the midi file.

* Cut down latency from changing mixer settings to hearing the change (this
  can be fixed a bit by tweaking the output plug-in settings, for most of
  the output plugins).