LUTs in Q31

[dukesrg]

Oscillator runtime API lookups are in float now, but OSC_CYCLE natively uses Q31 format.
This looks weird and leads to excessive calculations, like

• using f32_to_q31 with one FP multiplication per each sample is required
• clipping in +/-1.0 is needed per each sample in case several waves are combined, but not the case for saturated integer math, natively supported by ARM.

I did the test: reversed necessary funcitons of osc_api and float_math to Q31 math, made a precalculation of useneeded LUTs into Q31 format on oscillator init and used only integer math (including Q31) inside the OSC_CYCLE main loop. This gives roughly 50% performance increase. This really makes sence when you trying to combine dozens of waves in unison.

Maybe it is too late to change horses in midstream, but this could give a glue to performance optimization for someone.