Add Aux duty cycle as inputs to various tables for G4+

[Scott33]

I see G4x already has this feature, but it'd be great to add it to G4+, and I don't think it'd take much (if any) CPU resource to make it happen (unlike math channels).  Basically, if we could use the duty cycle of a GP PWM output of any aux output, then it'd allow for more complex logic when deciding boost, or accelerator position, or traction control slip target, or ...

As a corollary, it'd be nice if Virtual Aux had GP PWM capability too so the output of those tables could be used as well without having to dedicate an Aux output to this purpose.