patch::: 1.3.9.hwn2

pl 9.hwn1
	- abstracting Staff_symbol_referencer to an interface.
	- quantised_position for staccato dots.
	- standchen fixes
	- junk Score_element::do_{width,height}: set callbacks directly.
	- merge Score_element, Graphical_element
	- merge Axis_group_element, Graphical_axis_group
	- junk pointer fields from
	  * Single_malt_grouping_item
	  * Separating_group_spanner
	  * Stem_tremolo
	  * Hara_kiri_vertical_group_spanner
	  * Stem
	  * Axis_group_element
	  * Align_element
	  * Beam

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