First part of mf2pt1 adaption of parmesan noteheads.

First part of mf2pt1 adaption of parmesan noteheads.

Noteworthy changes:

  (draw_neomensural_brevis): Concatenate path fragments instead of adding
  subpictures.

  (find_tangent, find_tangent_shift): Two new macros, working iteratively.

  (draw_neomensural_longa): Use `find_tangent' to get a smooth transition
  between outline parts.

  (draw_diamond_head): Using `find_tangent_shift', the outline now exactly
  touches the bounding box.