added operator*=() to util/Matrix

git-svn-id: svn://anubis/fart/trunk@27 7f9b0f55-74a9-4bce-be96-3c2cd072584d

test/tests.cc

@@ -20,5 +20,11 @@ int main()
     Matrix mult = m * i;
     cout << "mult:" << endl << mult;
 
+    m *= m;
+    cout << "m^2:" << endl << m;
+
+    m *= m;
+    cout << "m^4:" << endl << m;
+
     return 0;
 }