Adenv crashes with segment times = 0

[andrewikenberry]

As dicussed on the Daisy forum.

[andrewikenberry]

Fix AdEnv non-zero issue

[sdiedrichsen]

This should have been fixed with my remake, which has been merge recently.

[makingsoundmachines]

I'm having some issues with the ADenv as it is right now:

• with long release times, a decay tied to a pot (via parameter) will sometimes get "stuck" and keep passing the audio through;
• with very short times close to 0.0 (e.g. 0.0001) and other DSP load going on, I get audio glitches that are gone at more moderate, "middle of the road" segment times

A suggestion (as discussed in the electrosmith slack) would be to apply @sdiedrichsen 's ADSR fix to the ADenv as well: #160

[makingsoundmachines]

A lower limit for segment values of 0.0005 (for ADENV_SEG_ATTACK / ADENV_SEG_DECAY) fixed the issues I was having.