Calculate the curve on the fly per the PSP.

Values based on lots of testing from the PSP, and match exactly.
Sustain defaults to 0, not 0x100.

Not sure how I came to that mistaken idea.
Fix integer overflow in exponent decrease.
Decay does not switch to release at height max.

This can happen with an exponent rate of 0.  It stays there.
Attack switches to decay at max height already.

It does not wait until it goes above.
Flip and shift instead of signed divide.

Clearer than all those zeroes and maybe faster...
Merge pull request #5402 from unknownbrackets/sas-minor

Update ADSR exponent curves and fix some small issues in ADSR