* lily/beam.cc: use length-fraction too.

* lily/beam.cc: use length-fraction too.

* scm/define-grob-properties.scm (all-user-grob-properties):
remove property flag-width-function
(all-user-grob-properties): remove space-function.

* scm/layout-beam.scm: remove flag-width-function.

* lily/beam.cc: remove flag-width-function

* scm/layout-beam.scm: remove beam dir functions.

* ly/engraver-init.ly (AncientRemoveEmptyStaffContext): use length-fraction.

* lily/beam.cc: remove dir-function.

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

* lily/beam.cc (calc_direction): use pseudo-property for beam
direction callback.
(calc_positions): use callback

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