More modulation sources for EG parameters

[christeck]

I miss a couple of modulation sources for the EGs. Examples:
- The sustain slope is a great parameter, but it immediately falls down after reaching its maximum value instead of remaining there. I thus wanted to modulate it by a slow triangle LFO (or maybe an other EG), but both aren't there.
- On another sound I wanted to add to the attack some value by a front panel button, but it isn't there either.
- Or a S&H LFO at minimum speed, to add some randomness.

[John Bowen]

Yes. there is a bug in the Sustain Slope in not staying on maximum. It was on the list long ago, but Klaus never got back to it.
Also, I had additional sources listed to modulate the EG segments, and hopefully these will all get extended at some point.