Add French-specific note names (issue 239930043 by address@hidden)

[v . villenave]

Reviewers: ,

Message:
Greetings everybody,
here’s an itch I’ve been wanting to scratch for the past decade or so:
as a French user, having to type "re" instead of "ré" feels unnatural
(and it still does after ten years); it is not uncommon that my scores
fail to compile because I’ve inadvertently typed "ré" somewhere in the
source code.

It’s also affecting newcomers to LilyPond, judging from my students; a
few years ago, I had added \language "français" as an alias to
"italiano" hoping that it would make things easier to explain, but that
particular oddity remains to this day.

I know that accented chars in the source code is not something
traditional coders want to have, but LilyPond has been utf8-based for
quite a while now so this shouldn’t be too disruptive a change.

Description:
Add French-specific note names

French users may (and do) want to enter the D pitch
as "ré" instead of Italian-like "re".

This also brings the -x double-sharp suffix to
French input language (an unrelated but welcome addition).

Please review this at https://codereview.appspot.com/239930043/

Affected files (+137, -10 lines):
  M Documentation/changes.tely
  M Documentation/notation/pitches.itely
  M input/regression/note-names.ly
  M python/convertrules.py
  M python/musicexp.py
  M scm/define-note-names.scm