Revision 4020

* SFZ engine: Fixed wrong velocity for release triggered samples: if and
  only if note-off velocity is exactly zero (which means MIDI keyboard
  does not have release velocity sensors) then use previous note-on
  velocity as note-off velocity for release triggered samples instead
  (regression of SVN r4013).

* Gig engine: Fixed wrong velocity for release triggered samples: if and
  only if note-off velocity is exactly zero (which means MIDI keyboard
  does not have release velocity sensors) then use previous note-on
  velocity as note-off velocity for release triggered samples instead 
  (regression of SVN r2879).

* Bumped version (2.2.0.svn15).