Bugfix for issue 1630 (issue4490045)

[lemniskata . bernoullego]

Reviewers: karin_hoethker.de, Graham Percival, lemzwerg,  
carl.d.sorensen_gmail.com,

Message:
Finally i'm back in Warsaw and i'm uploading Karin's patch. Sorry for
the delay :(

Here's an archive with test file and output pdfs from before and after
the patch: http://www.sendspace.com/file/gog5zh

I see that Carl's comments written in issue tracker are now resolved
(commenting style and scm properties), so the patch is ready for
discussion i think.

Again, my apologies for the delay!

Janek

Description:
Bugfix for issue 1630

Remove duplicate ties for chords autosplit with
Completion_heads_engraver and manually tied.

Please review this at http://codereview.appspot.com/4490045/

Affected files:
  M lily/completion-note-heads-engraver.cc
  M lily/tie-engraver.cc
  M scm/define-music-properties.scm