feature request: \mark avoiding notes

[Graham Percival]

Personal feature request here, not anything from the manual.

Would it be possible to make \mark avoid notes?  I'm converting
some c^\markup to c^\mark \markup  , and I have to start guessing
manual #'padding numbers again.  Could you just take the collision
avoidance code for \markup and apply it to \mark ?

Cheers,
- Graham

\layout{ raggedright=##t}
\relative c'''{
c4 d e d
\once \override Score.RehearsalMark #'self-alignment-X = #right
\once \override Score.RehearsalMark #'break-visibility = 
#begin-of-line-invisible
\mark \markup{ \bold { D.S. al Fine }}
}