Potential fix for issue 1504. (issue4237057)

[hanwenn]

http://codereview.appspot.com/4237057/diff/1/lily/beam.cc
File lily/beam.cc (right):

http://codereview.appspot.com/4237057/diff/1/lily/beam.cc#newcode173
lily/beam.cc:173: span_data.push_back (get_beam_span
(orig->broken_intos_[i], commonx));
this looks wrong - different broken pieces cannot ever share a commonx.

http://codereview.appspot.com/4237057/diff/1/lily/spanner.cc
File lily/spanner.cc (right):

http://codereview.appspot.com/4237057/diff/1/lily/spanner.cc#newcode405
lily/spanner.cc:405: Spanner::broken_spanner_index (Spanner const *sp)
why not make it a real member funtcion?

http://codereview.appspot.com/4237057/