Investigate Frobenius Additive FFT

> I believe this can be a drop-in replacement for the FFT that is currently being used:
> https://arxiv.org/pdf/1802.03932.pdf
>
> More background:
> http://www.texmacs.org/joris/ffft/ffft.pdf

> ~5x faster for 16-bit field, ~3x faster for 8-bit field hypothetically

https://github.com/catid/leopard/issues/5