remove all the _Order mechanics, now we are always traversing matrices in

column-major order, even if storage is row-major. Benchmark showed that adapting
the traversal order to the storage order brought no benefit.

Also do some cleanup after Gael's big patch.

Eigen/src/Core/Product.h

@@ -75,7 +75,6 @@ template<typename Lhs, typename Rhs> class Product : NoOperatorEquals,
       assert(lhs.cols() == rhs.rows());
     }
     
-    static const TraversalOrder Order = Lhs::Order;
     static const int RowsAtCompileTime = Lhs::RowsAtCompileTime,
                      ColsAtCompileTime = Rhs::ColsAtCompileTime;