Mark collisions

[John Galbraith]

I have a bunch of marks created with \Mark.  I push them a little bit 
higher with 

RehearsalMark \override #'padding = #3.5

in the OrchestralScoreContext translator block.  This avoids most of the
collisions, but is a bit higher than I would like and still collides
sometimes with high notes.  If I bring it any lower it also likes
to collide with the multimeasure rest counts on the parts, among other
things.  Are RehearsalMarks somehow exempt from the other collision
detection algorithms?  I noticed that I rarely ever see collisions anymore
anywhere else (even in dynamics - Yay!).

I guess I could manually change the RehearsalMark padding every time,
but this is a pain because I use the same global mark track for both
parts and the conductor's score and the ideal padding is often different
in the two cases.  Plus, it would be better in general not to have to
micromanage things like that (which Lilypond is usually great at doing
for me).

John