* rehearsalmark-horiz-extent.ly: add note.

* rehearsalmark-horiz-extent.ly: add note.

* scm/music-functions.scm (glue-mm-rest-texts): also put other
events into EventChord. This fixes textspanners on mm rests.

* lily/side-position-interface.cc (get_axis): read side-axis
(set_axis): set side-axis.

* scm/define-grobs.scm (all-grob-descriptions): add side-axis
properties everywhere.

* lily/spacing-spanner.cc (breakable_column_spacing): add
average-spacing-wishes. Take maximum if not set.
(musical_column_spacing): idem.

* scm/define-grobs.scm (all-grob-descriptions): add average-spacing-wishes.

* lily/grob-closure.cc (add_offset_callback): bugfix: properly add
offset callbacks. This fixes alignment for Fingering objects.

* scm/define-grobs.scm (all-grob-descriptions): tiny bit less
space for key - timesig combination.

* scm/define-grobs.scm (all-grob-descriptions): decrease distance
to key sig.

* scm/define-grobs.scm (all-grob-descriptions): remove
self-X-offset. Fixes alignment of octavate-8.