* input/regression/rehearsal-mark-number.ly: new file.

* input/regression/rehearsal-mark-number.ly: new file.

* input/regression/rehearsal-mark-letter.ly: new file.

* scm/translation-functions.scm (number->mark-string): new function
(format-mark-letters): new function
(format-mark-numbers): new function

* lily/mark-engraver.cc (process_music): rehearsalMark is now
integer; formatting is done through markFormatter property.

* scm/define-translator-properties.scm: fold all *-done properties
into positioning-done.

* lily/beam.cc (position_beam): new function
(brew_molecule): make sure that positions are calced before making
the molecule.

* ps/music-drawing-routines.ps: take blot as 4th argument.

* lily/beam.cc (brew_molecule): fix beam offsets: overlap with the
stem do avoid small dents.