PLZ replace smat4_g in c file with smat4_look_at

[heitaoflower]

PLZ replace smat4_g in c file with smat4_look_at, Thanks.

By the way , I was wondering if you have any plan to maintain the repo, I am keen on seeing that you guy adding SIMD in it.

[felselva]

Thanks! ps* and s* functions were generated using a script. There was probably a problem with the parser that named the function smat4_g.

I want to eventually add SIMD option.