* lily/spacing-determine-loose-columns.cc: new file.

* lily/spacing-determine-loose-columns.cc: new file.

* input/regression/spacing-strict-notespacing.ly: new file.

* lily/spacing-spanner.cc (generate_springs): rename from
do_measure.
(generate_pair_spacing): new function.
(init, generate_pair_spacing): set between-cols for floating
nonmusical columns.

* lily/spaceable-grob.cc (get_spring): new function.

* lily/tuplet-bracket.cc (print): on the left, the overshoot is
relative to the right edge of the prefatory matter.

* lily/beam.cc (print): read break-overshoot to determine where to
stop/start broken beams.