release: 1.3.68

release: 1.3.68

======

* ly2dvi: changed back to original semantics of latexheaders.

* Stem_tremolo, Crescendo, Hara_kiri_group_spanner, Tuplet_spanner,
Volta_spanner changed into interface.

* Related cleanups for Tie, Tie_column cleanups.

* Made Time_signature, Single_malt_grouping_item, Script_column,
Chord_name, Dot_column, Breathing_sign, Key_item type into interface.

* Removed const declaration from callback arguments.

* Pagebreak support. See input/test/between-systems.ly

* Fixed a problem with accidentals in combination with
non-nil key signatures.

1.3