tremolo slope on knees

[Rune Zedeler]

I don't know whether this is a bug or a feature, but I think it looks a 
bit strange that tremolos get the same slope as the beams to which they 
are connected. Would prefer them to get the "default" slope - this would 
also make them easier to distinguish from beams.

\score {
\notes { [g'8:32 g'] [g'8:32 g] g'4:32  }
}

-Rune