`fract` function

[SolitudeSF]

I was trying to port some glsl shaders with shady, but i discovered that vmath doesnt provide fract function. It does provide fractional proc for floats only, and doesnt generate vector variant, so i dont know what is the intended way for its inclusion and parity with glsl. not a big deal, since we have floor, but annoying anyway.

[treeform]

I have run into this as well I will be renaming fractional to fract and adding support for vectors soon.

[treeform]

#66