Overhauls broken bound coordinate checking (issue 5602054)

[n . puttock]

http://codereview.appspot.com/5602054/diff/2001/input/regression/metronome-mark-broken-bound.ly
File input/regression/metronome-mark-broken-bound.ly (right):

http://codereview.appspot.com/5602054/diff/2001/input/regression/metronome-mark-broken-bound.ly#newcode1
input/regression/metronome-mark-broken-bound.ly:1: \version "2.15.27"
2.15.28

http://codereview.appspot.com/5602054/diff/2001/input/regression/metronome-mark-broken-bound.ly#newcode4
input/regression/metronome-mark-broken-bound.ly:4: texidoc = "A broken
spanner must not interfere with @code{\\tempo}
Surely you mean break-alignable grobs shouldn't interfere with broken
spanners?  You have this back-to-front.

http://codereview.appspot.com/5602054/diff/2001/input/regression/metronome-mark-broken-bound.ly#newcode12
input/regression/metronome-mark-broken-bound.ly:12: \tempo \markup {
"fooooo" } 4 = 90
You might add

\override Score.MetronomeMark #'break-visibility = #all-visible

otherwise you're only checking the left-broken spanners.

http://codereview.appspot.com/5602054/diff/2001/input/regression/metronome-mark-broken-bound.ly#newcode22
input/regression/metronome-mark-broken-bound.ly:22: \ottava #1 \times
1/1 { e'8\<\startTextSpan\startTrillSpan\glissando\episemInitium
If you want to test episema, you need to add the engraver (it's not
worth it imo
since you wouldn't use it outside a VaticanaVoice and it would never be
broken).

The code's a bit messy here

http://codereview.appspot.com/5602054/diff/2001/scm/define-grobs.scm
File scm/define-grobs.scm (right):

http://codereview.appspot.com/5602054/diff/2001/scm/define-grobs.scm#newcode1420
scm/define-grobs.scm:1420: (bound-alignment-forbidden-interfaces .
(metronome-mark-interface))
I question whether you need this property.  Would be better just to
exclude break-alignable-interface in axis-group-interface.cc (so it
includes RehearsalMark and BarNumber - note that these will also
interfere with bounds if you leave them out here)

http://codereview.appspot.com/5602054/