Revision 1687

- added new LSCP event "CHANNEL_MIDI" which can be used by frontends to
  react on MIDI data arriving on certain sampler channels (so far only
  Note-On and Note-Off events are sent via this LSCP event)
- bumped LSCP compliance version to 1.4
- bumped LS version to 0.5.1.3cvs