Math.sh done right

[everettmcarpenter]

I have included a clean push of all changes for Math.sh(), only changing core files.

@gewang

[everettmcarpenter]

This build has been tested and confirmed to be working on an Intel Mac, Ubuntu machine and Windows as of 02/21

[gewang]

thank you! we will go ahead and merge;
as follow-ups, we would ask for one or more tests examples (with expected output); also, could you provide a link or brief explanation for the "magic constants" used in ck_associated_legendre()

[everettmcarpenter]

hello @gewang , wonderful! thank you for allowing me to be a part of ChucK. I will open a PR with some examples and display .sh()'s functionality with some calculation examples as well as ambisonic encoding via Gain[].

as for ck_associated_legendre(), here are some explanations of the terms used in it, the definitions are taken from Wolfram (5th order was dervied by myself using their definition containing derivatives of legendre polynomials). the "magic constants" are from the definition of associated legendre polynomials, which can be seen in the above link.

flip is a nifty relation for associated legendre polynomials with negative degrees, which can be read about more here Associated Legendre Polynomials with Negative degree and/or order