#4815 Matrix ordered incorrectly in sums and products

[David Scherfgen]

(%i1) declare(v, nonscalar)$

(%i2) expr : v + matrix([1]);
(%o2) v + matrix([1])

(%i3) expr + matrix([1]);
(%o3) v + matrix([1]) + matrix([1])

The correct output for (%o3) is v + matrix([2]).

The exact same bug exists for products:

(%i4) expr : v * matrix([1]);
(%o4) v * matrix([1])

(%i5) expr * matrix([1]);
(%o5) v * matrix([1]) * matrix([1])