* lily/script-engraver.cc (make_script_from_event): don't trigger callback.

* lily/script-engraver.cc (make_script_from_event): don't trigger callback.

* lily/item-scheme.cc: new file.

* lily/bar-line.cc (before_line_breaking): remove function.
remove bar-size-procedure, break-glyph-function

* lily/clef-engraver.cc (set_glyph): use glyph iso. glyph-name

* lily/clef.cc (before_line_breaking): change to calc_glyph_name.

* lily/system-start-delimiter.cc (print): suicide from
here. Remove after_line_breaking_callback.

* lily/script-interface.cc (calc_direction): use callback for direction.

* lily/side-position-interface.cc (aligned_side): don't use
Side_position_interface::get_direction directly. Use callback.

* scm/define-grobs.scm: change print-function to stencil callback everywhere.

* scm/define-grob-properties.scm (all-user-grob-properties): doc
callbacks property.