Compare traversal for memoization before bound nodes container

  ast_type_traits::TraversalKind Traversal = ast_type_traits::TK_AsIs;

  bool operator<(const MatchKey &Other) const {

    return std::tie(MatcherID, Node, BoundNodes, Traversal) <

           std::tie(Other.MatcherID, Other.Node, Other.BoundNodes,

                    Other.Traversal);

    return std::tie(Traversal, MatcherID, Node, BoundNodes) <

           std::tie(Other.Traversal, Other.MatcherID, Other.Node,

            Other.BoundNodes);

  }

};