* lily/simple-spacer.cc: Remove class Simple_spacer_wrapper.

	* lily/simple-spacer.cc: Remove class Simple_spacer_wrapper.
	Replace it with functions get_line_forces and get_line_configuration.
	(class Simple_spacer): Make data private.
	Rewrite compression algorithm to be faster and simpler.

	* lily/simple-spacer-scheme.cc (ly_solve_rod_and_spring_problem):
	* lily/gourlay-breaking.cc (solve):
	* lily/constrained_breaking.cc (space_line):
	Change it to the new simple-spacer code.

	* lily/paper-score.cc (get_paper_systems):
	(Paper_score):
	(process):
	Delay breaking the systems until they are requested.
	(find_break_indices):
	Use vsize for indices.
	(calc_breaking):
	Move the "Calculating line breaks" message here.

	* lily/system.cc (pre_processing):
	Move the "Calculating line breaks" message away from here.
	(break_into_pieces):
	Allow multiple calls to this function in sequence (with touching-but-
	not-overlapping breakpoints).

	* lily/constrained-breaking.cc:
	Replace most of the get_XXXX functions with get_line_details.
	Only calculate the force for each line. Calculate configurations only
	for the lines we will actually use.
	Replace cols_ with lines_.