Issue 5272: Add \depart <markup> (issue 337520043 by address@hidden)

[nine . fierce . ballads]

Reviewers: ,

Message:
I would be happy to hear suggestions for the name of this command.

My opinion is that \depart is a reasonable name when used for the likes
of D.C., D.S., and "2nd time to Coda" but \depart "Fine" is slightly
weird (departing to nowhere?).


Description:
https://sourceforge.net/p/testlilyissues/issues/5272/

Add \depart <markup> command to make it unnecessary to continue abusing
rehearsal marks for instructions such as "D.C."  It solves these
problems that rehearsal marks alone could not solve:

* It is possible to change the default direction of departure marks
  without changing the default direction of rehearsal marks.

* It is possible to use a departure mark and a rehearsal mark at the
  same moment.

Please review this at https://codereview.appspot.com/337520043/

Affected files (+293, -0 lines):
  M Documentation/changes.tely
  A input/regression/departure-mark-instrumental.ly
  A input/regression/departure-mark-vocal.ly
  A lily/departure-mark-engraver.cc
  M ly/engraver-init.ly
  M ly/music-functions-init.ly
  M scm/define-event-classes.scm
  M scm/define-grobs.scm
  M scm/define-music-types.scm