Issue 1278: Arrow notation for quarter-tones. (issue3789044)

[FelipeG . Assis]

Reviewers: ,

Message:
This patch is first and foremost a change in the internal Pitch
representation. I then suggest that we first discuss that, having it as
a reference.

Description:
Issue 1278: Arrow notation for quarter-tones.

We change the internal pitch representation so as to account for two
levels of alteration. Basically, instead of representing alterations
by a rational number, we represent them by a pair of integers.

The main changes are the addition of an Alteration struct, and
modifications in the Pitch and Scale classes.

The Pitch class was reimplemented. Its interface was mostly preserved.
No pitch normalisation policy is implemented, though.
(see lily/include/pitch.hh and lily/pitch.cc)

Class Scale was completely rewritten.
(see lily/include/scale.hh and lily/scale.hh)

Finally, new note names are defined, and the arrow style accidentals
are made available via the new arrow-alteration-glyph-name-alist.
(see scm/lily-library.scm, scm/define-note-names.scm and
scm/output-lib.scm)

Other changes are basically simple side-effects of these.

Please review this at http://codereview.appspot.com/3789044/

Affected files:
  M input/regression/scheme-book-scores.ly
  M lily/accidental-engraver.cc
  M lily/accidental-placement.cc
  A lily/alteration.cc
  M lily/ambitus-engraver.cc
  A lily/include/alteration.hh
  M lily/include/lily-guile.hh
  M lily/include/pitch.hh
  M lily/include/scale.hh
  M lily/key-engraver.cc
  M lily/key-performer.cc
  M lily/key-signature-interface.cc
  M lily/lily-guile.cc
  M lily/music-scheme.cc
  M lily/music.cc
  M lily/parser.yy
  M lily/pitch-scheme.cc
  M lily/pitch.cc
  M lily/pitched-trill-engraver.cc
  M lily/scale.cc
  M lily/slur-scoring.cc
  M ly/engraver-init.ly
  M ly/makam.ly
  M ly/scale-definitions-init.ly
  scm/chord-entry.scm
  scm/chord-generic-names.scm
  scm/chord-ignatzek-names.scm
  scm/chord-name.scm
  scm/define-grob-properties.scm
  scm/define-markup-commands.scm
  scm/define-music-display-methods.scm
  scm/define-music-properties.scm
  scm/define-note-names.scm
  scm/lily-library.scm
  scm/lily.scm
  scm/midi.scm
  scm/music-functions.scm
  scm/output-lib.scm
  scm/tablature.scm
  scm/translation-functions.scm