[PATCH] Clef support for cue notes

[Reinhold Kainhofer]

Clef support for cue notes

-) Added \cleffedCueDuring, which allows to specify a clef for
   the cue notes. At the end of the cue section, the clef is
   automatically reset to the containing voice's clef.
-) Cue clefs are implemented as CueClef and CueEndClef grobs,
   created by a dedicated Cue_clef_engraver, which reads
   some cueClef* context properties.
-) After a line break, a cue clef does NOT override the global clef
   of the containing voice, but prints (in smaller size) after
   the containing clef.

http://codereview.appspot.com/2726043/

Regtest showing how things work is included.

Please review,
Reinhold

-- 
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Reinhold Kainhofer, address@hidden, http://reinhold.kainhofer.com/
 * Financial & Actuarial Math., Vienna Univ. of Technology, Austria
 * http://www.fam.tuwien.ac.at/, DVR: 0005886
 * LilyPond, Music typesetting, http://www.lilypond.org