* Documentation/topdocs/NEWS.tely (Top): mention John Mandereau.

* Documentation/topdocs/NEWS.tely (Top): mention John Mandereau.
(Top): document #'callbacks.
(Top): document nested \override.

* input/regression/figured-bass.ly: update for slash and pluses.

* input/regression/figured-bass-continuation-forbid.ly (Module):
new file.

* scm/translation-functions.scm (format-new-bass-figure): use
slashed-digit if diminished is set.
(format-new-bass-figure): add + if 'augmented is set.

* scm/define-markup-commands.scm (slashed-digit): new command slashed-digit.

* input/test/piano-staff-distance.ly: remove file.

* Documentation/user/advanced-notation.itely (Formatting cue
notes): use length-fraction for making stems/beams smaller.

* lily/parser.yy (bass_figure): accept \+ \! and / as figured bass
modifications.

* lily/new-figured-bass-engraver.cc: new property
centerFiguredBassContinuations

* Documentation/user/changing-defaults.itely (Difficult tweaks):
use callbacks.

* python/convertrules.py (FatalConversionError.subber): conversion
rule for #'callbacks

* lily/parser.yy (music_property_def): allow \override #'a #'b =
#c too.