message: Don't use std::iterator; it's deprecated in C++17
diff: @@ -30,8 +30,13 @@ namespace ranges
  {
  template<typename T>
  struct movable_input_iterator
  - : std::iterator<std::input_iterator_tag, T, std::ptrdiff_t, T *, T &&>
  {
  + using iterator_category = std::input_iterator_tag;
  + using value_type = T;
  + using difference_type = std::ptrdiff_t;
  + using pointer = T *;
  + using reference = T &&;
  +
  movable_input_iterator() = default;
  movable_input_iterator &operator++();
  movable_input_iterator operator++(int);
  