Please add symath

[hemml]

https://github.com/hemml/symath

A simple (and rather fast) symbolic math package for Common Lisp. I'm using it in my CFD-code generation project (not published yet), where it deals with huge expressions with thousands of terms, sometimes reducing their sizes to dozens of terms.

Now it implements only algebraic simplification (the most complicated operation in my practice), but will be extended later to implement simple solving, etc.