\break and grace timing

[Erik Sandberg]

As Will Oram pointed out, there are problems when \break occur near grace 
notes.

In this example, the second but not the first score does a line break:

\version "2.3.11"
A = \new Staff \notes {c1 | \grace c8 c1 }
B = \new Staff \notes {c1 | \break c1 }
\book {
  \score {<<\A \B>>}
  \score {\B}
}

I consider this a bug.

I have been thinking about how it best would be solved. My conclusion is that 
the cleanest way would be to add a timestep that happens right before all 
grace note timing. I.e. in the case
c1 | \break \grace c8 d1
the c1 would be at time 0 in the first bar, the \break at the new time 0-inf 
in the second bar, the c8 at time 0-1/8, and the d1 at time 0 in the second 
bar. 

Another possibility (which I however don't find as clean) is to let the \break 
command search for grace notes in all other staves, and move itself to a spot 
right before them.

Any opinions, developers? I'll add this as a bug if you don't protest.

Erik