Math.atan should bail when term reaches Infinity

https://github.com/CanadaHonk/porffor/blob/eed7f811bc07864909fa39e74d21760a932f3244/compiler/builtins/math.ts#L438-L444 can infinite loop if it doesn't bail when the term goes non-finite: ```mjs if (term == Infinity) return Math.PI / 2 if (term == -Infinity) return -Math.PI / 2; ``` Is a potential fix