mat4.multiply fix parameter order to be logical, matR,matL -> matL,matR

[cjcliffe]

Now that the math library is in a much better state it's probably a good time to fix up the logically reversed order on the mat4.multiply function that was carried over from my old C++ software rendering stack -- it's origin isn't CubicVR C++ since it used the OpenGL matrix stack exclusively at the time which is why I needed to quickly grab an old implementation I had available for porting :)