* fix compilation issue in Product

* added some tests for product and swap
* overload .swap() for dynamic-sized matrix of same size

test/basicstuff.cpp

@@ -82,6 +82,12 @@ template<typename MatrixType> void basicStuff(const MatrixType& m)
   {
     VERIFY_RAISES_ASSERT(m1 = (m2.block(0,0, rows-1, cols-1)));
   }
+
+  // test swap
+  m3 = m1;
+  m1.swap(m2);
+  VERIFY_IS_APPROX(m3, m2);
+  VERIFY_IS_NOT_APPROX(m3, m1);
 }
 
 void test_basicstuff()