NOTEON handler invocation is deffered

[dukesrg]

Tried to implement a software voice assignment on NTS-1 and failed. Looks like NOTEON handler is delayed untill oscillator is currently in progress so it is virtually impossible to mix a polyphonic sound inside CYCLE handler. I realize this is something out of the scope of the device specification but anyway there is a reasonable question how actually NOTEON/NOTEOFF handlers are expected to work.

[dukesrg]

@etienne-korg With firmware 1.20 and Legato=off, NOTEON event is exposed to the oscillator - now oscillators can be crafted to produce real chord! But EG is triggered every time NOTEON is received. And still only the last NOTEOFF is exposed, regardless of the poly mode (CC127).

Also it would be better to have legato control at standard CC68, and maybe keep the current global setting to invert the CC action for the sake of compatibility.