Multiplies the two supplied matrices together and stores the resulting matrix inside this.
<note>It is possible to multiply the a matrix in-place, so this can be equal to
a but can't be equal to b.</note>
| this |
The address of a 4x4 matrix to store the result in |
| a |
A 4x4 transformation matrix |
| b |
A 4x4 transformation matrix |