_m expects the matrix that is to premultiply the current matrix.
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
mmmmuuuullllttttmmmmaaaattttrrrriiiixxxx premultiplies the current matrix, as specified by mmmmmmmmooooddddeeee, by
the 4x4 floating point matrix _m. Thus if _T is the current matrix,
mmmmuuuullllttttmmmmaaaattttrrrriiiixxxx((((_M)))) replaces _T with _M*_T. The current matrix is the top matrix
on the transformation stack if mmmmmmmmooooddddeeee is MMMMSSSSIIIINNNNGGGGLLLLEEEE, the top matrix on the
ModelView matrix stack if mmmmmmmmooooddddeeee is MMMMVVVVIIIIEEEEWWWWIIIINNNNGGGG, the Projection matrix if
mmmmmmmmooooddddeeee is MMMMPPPPRRRROOOOJJJJEEEECCCCTTTTIIIIOOOONNNN, or the Texture matrix if mmmmmmmmooooddddeeee is MMMMTTTTEEEEXXXXTTTTUUUURRRREEEE.