message: type_traits: Add `remove_cvref_t` alias, in anticipation of C++20.
diff: @@ -22,6 +22,10 @@ namespace std
  template <typename T>
  using remove_cv_reference_t = typename remove_cv_reference<T>::type;
  + /// C++20 proposal
  + template <typename T>
  + using remove_cvref_t = typename remove_cv_reference<T>::type;
  +
  template <typename T>
  struct identity
  {
  