* lily/multi-measure-rest-engraver.cc: use a single

* lily/multi-measure-rest-engraver.cc: use a single
MultiMeasureEvent for mm rests. This prevents problems with the
new part combiner.

* scm/music-functions.scm (determine-split-list): analysis has
global effect: a difference halfway a phrase makes the entire
phrase be typeset as apart.
(make-multi-measure-rest): make mmrest as a single rhythmic event.