Issue 461: LilyPond should accept a tie between notes which are enharmonically identical

Issue 461: LilyPond should accept a tie between notes which are enharmonically identical

This patch connects the respective notes in Tie_engraver and
Tie_performer as a fallback after exhausting regular tie associations.
It also keeps the accidental engraver from applying its special rules
for tied notes that don't have exactly matching pitches.

No attempt is made to adjust the visuals of the ties: they will remain
horizontal, focused on the left note head.

[lemzwerg, 2014-10-18 14:50:58]

Very nice!  Thanks for implementing this feature.  LGTM.

[uliska, 2014-10-18 18:02:15]

LGTM too.

Of course this doesn't look right out-of-the-box (maybe it would be good to let
the Tie being printed as a Slur instead). But as one can use \shape it's at
least possible to use that as a working and semantically correct solution.
It even works with cross-staff ties (although I suspect that their layout is
very fragile).