[CM] CMN - "vibrato" strangeness

[Bill Schottstaedt]

> (cmn (staff treble (g4 h vibrato)))
> lisp cpu usage goes up to 99% and the repl just hangs until i interrupt lisp 

Thanks for the bug report!  It is indeed an infinite loop caused, I think,
by the fact that it doesn't find a good endpoint for the mark.  Here's
a quick fix:  in accent.lisp, line 445 (I think -- I'm using an editor I'm
not used to), change

(ct (round (- (box-x1 vib) x0 .75) wid)))

to 

(ct (max 1 (round (- (box-x1 vib) x0 .75) wid))))