MIDI Marker feature request

[Keith Smith]

It would be very useful if lilypond had the ability to add MIDI markers
to the MIDI output.  Currently, the structure of a song is difficult to
produce in MIDI as only \unfoldrepeats is available and constructs like
D.S. al coda, are not understood.  If MIDI markers could be added then
it would be easier to import the MIDI file into a DAW and find where
sections of the composition need to be cut, moved, copied, etc. so that
the complete structure of the composition can be more easily
constructed.

Thanks, Keith