* lily/tie.cc: change 'heads to 'head-pair.

* lily/tie.cc: change 'heads to 'head-pair.

* lily/lyric-phrasing-engraver.cc (process_acknowledged_grobs):
fill in 'heads field.

* lily/lyric-extender.cc (brew_molecule): use heads for width, use
minimum-length for short ones, and shorten so collisions with the
next syllable are avoided.

* lily/beam-quanting.cc (score_slopes_dy): add extra points for
near-zero slopes.
Only do DAMPING_DIRECTION_PENALTY for non-horizontal dy

* lily/dots.cc: remove quantized_position callback. All Y
positioning is done by dot-column.cc

* lily/dot-column.cc (do_shifts): rewrite shifting routine: do
exhaustive test of all dot positions. This fixes disappearing dots
in dotted chords.