Enable use of evaluators for noalias and lazyProduct, add conversion to scalar for inner products

Eigen/src/Core/util/ForwardDeclarations.h

@@ -36,6 +36,12 @@ template<typename Derived> struct accessors_level
   };
 };
 
+template<typename T> struct evaluator_traits;
+
+template< typename T,
+          typename Kind = typename evaluator_traits<T>::Kind,
+          typename Scalar = typename T::Scalar> struct evaluator;
+
 } // end namespace internal
 
 template<typename T> struct NumTraits;