Re: Align metronome mark at time signature or first musical element. Fixes #684. (issue1579041)

[hanwenn]

http://codereview.appspot.com/1579041/diff/42001/43004
File lily/metronome-engraver.cc (right):

http://codereview.appspot.com/1579041/diff/42001/43004#newcode81
lily/metronome-engraver.cc:81: }
is there a reason you are worried about cyclical data structures?  I
don't think we check for them anywhere else.

http://codereview.appspot.com/1579041/