message: Add missing type aliases to cow_vector
diff: @@ -19,12 +19,16 @@ class cow_vector {
  public:
  // -- member types -----------------------------------------------------------
  - using std_type = std::vector<T>;
  + using value_type = T;
  +
  + using std_type = std::vector<value_type>;
  using size_type = typename std_type::size_type;
  using const_iterator = typename std_type::const_iterator;
  + using difference_type = typename std_type::difference_type;
  +
  using const_reverse_iterator = typename std_type::const_reverse_iterator;
  // -- constructors, destructors, and assignment operators --------------------
  