Prevents script tie collisions (issue 6500058)

[k-ohara5a5a]

I can't get it to work for the script at the start of the tie.
\relative c''' { r2. c4~-> | c-> r2. }


http://codereview.appspot.com/6500058/diff/1/input/regression/script-tie.ly
File input/regression/script-tie.ly (right):

http://codereview.appspot.com/6500058/diff/1/input/regression/script-tie.ly#newcode10
input/regression/script-tie.ly:10: r2. c4 ~ |
r2. c4-> ~

http://codereview.appspot.com/6500058/diff/1/lily/script-engraver.cc
File lily/script-engraver.cc (right):

http://codereview.appspot.com/6500058/diff/1/lily/script-engraver.cc#newcode54
lily/script-engraver.cc:54: set<Grob *> ties_;
Ties only affect the note at their beginning and at their end, so I do
not see the need to remember them.   Can't you just add them to the
support of a script immediately upon acknowledging their beginnings and
ends?

http://codereview.appspot.com/6500058/diff/1/lily/script-engraver.cc#newcode226
lily/script-engraver.cc:226: ties_.erase (ties_to_remove_[i]);
It looks, to me, like you erase any tie ending on this note /before/ you
tell any scripts on this not about the tie.
However, it works at this end of the tie so I must be misunderstanding
something.

http://codereview.appspot.com/6500058/