[PATCH] Move left-broken line-spanner check to after-line-breaking callback

[Neil Puttock]

Hi,

Currently left-broken line spanners and hairpins are removed
automatically if they end on the first note.  Though this is usually
appropriate for trills, glissandi and hairpins, there are situations
where it would be useful to override this default behaviour, for
example when using text spans.

This patch moves the hard-coded check from Line_spanner::print () to a
new callback, ly:spanner::after-line-breaking, which can be set as
required.

Please review the patch here:

http://codereview.appspot.com/32148/show

Cheers,
Neil