#2175 ratmx and matrix_element_mult

[Barton Willis]

When ratmx is true, a nondefault value for matrix_element_mult does not work correctly; example

(%i275) a : matrix([matrix([1,3],[0,2]),matrix([4,4],[1,1])],[matrix([4,0],[3,3]),matrix([3,3],[4,0])]);
(%o275) matrix([matrix([1,3],[0,2]),matrix([4,4],[1,1])],[matrix([4,0],[3,3]),matrix([3,3],[4,0])])
(%i276) a.a, ratmx : true, matrix_element_mult : ".";
(%o276)/R/ matrix([matrix([1,3],[0,2])^2+matrix([4,0],[3,3])*matrix([4,4],[1,1]),matrix([4,4],[1,1])*matrix([1,3],[0,2])+matrix([3,3],[4,0])*matrix([4,4],[1,1])],[matrix([4,0],[3,3])*matrix([1,3],[0,2])+matrix([3,3],[4,0])*matrix([4,0],[3,3]),matrix([4,0],[3,3])*matrix([4,4],[1,1])+matrix([3,3],[4,0])^2])

See also bug 1911030