speed has no effect on synths and soundfonts

[felixroos]

probably makes sense to make it have an effect, just as a frequency multiplier, so functions like hurry would work as expected.
in the case of soundfonts, it should make sense to multiply it with the frequency after the sample has been selected, so that the repitch actually sounds like a repitch, instead of getting a sample in a different zone.
this is a breaking change but might not affect a lot of patterns

[yaxu]

Superdirt takes the absolute value of speed before multiplying, probably makes sense, although might it also be nice to reverse the envelopes for negative speeds somehow..

https://github.com/musikinformatik/SuperDirt/blob/c7f32998572984705d340e7c1b9ed9ad998a39b6/classes/SuperDirtUGens.sc#L159-L169