Improves some parmesan noteheads. (issue 4639065)

[bordage . bertrand]

Reviewers: ,

Message:
Hi everyone,

This patch is finally ready for review!

What has been done for Petrucci/mensural/neomensural:
* Stems centered around the attachment point.
* Attachment point lowered.
* Brevis/longa/maxima pointing downward.
* Use the left-stemmed longa in ligatures.
* A larger hole height for brevis/longa/maxima on staff line.

What has been done for Petrucci only:
* Better notehead design.

Regards,
Bertrand

Description:
Improves some parmesan noteheads.

Please review this at http://codereview.appspot.com/4639065/

Affected files:
  M input/regression/note-head-style.ly
  M lily/mensural-ligature.cc
  M lily/note-head.cc
  M lily/stem.cc
  M ly/engraver-init.ly
  M mf/GNUmakefile
  M mf/parmesan-generic.mf
  A mf/parmesan-noteheads-generic.mf
  M mf/parmesan-noteheads.mf
  A mf/parmesan-noteheads11.mf
  A mf/parmesan-noteheads13.mf
  A mf/parmesan-noteheads14.mf
  A mf/parmesan-noteheads16.mf
  A mf/parmesan-noteheads18.mf
  A mf/parmesan-noteheads20.mf
  A mf/parmesan-noteheads23.mf
  A mf/parmesan-noteheads26.mf
  M scripts/build/gen-emmentaler-scripts.py
  M scripts/build/mf-to-table.py