Merge branch 'master' of ssh://jomand@git.sv.gnu.org/srv/git/lilypond

* 'master' of ssh://jomand@git.sv.gnu.org/srv/git/lilypond:
  MusicXML: Convert accordion registrations
  MusicXML: Implement rehearsal marks and some more spanners
  Minor tweak to output.
  Update from Ralph.
  MusicXML: (Test cases) Make Finale happy (very picky about correct syntax..)
  Update from Trevor.