message: rename __static_const to _static_const (reserved identifier)
diff: @@ -220,18 +220,18 @@ struct DecimalSeparator : std::numpunct<char>
  // taken from ranges-v3
  // TODO add doc
  template <typename T>
  -struct __static_const
  +struct _static_const
  {
  static constexpr T value{};
  };
  template <typename T>
  -constexpr T __static_const<T>::value;
  +constexpr T _static_const<T>::value;
  inline namespace
  {
  - constexpr auto const& to_json = __static_const<detail::to_json_fn>::value;
  - constexpr auto const& from_json = __static_const<detail::from_json_fn>::value;
  + constexpr auto const& to_json = _static_const<detail::to_json_fn>::value;
  + constexpr auto const& from_json = _static_const<detail::from_json_fn>::value;
  }
  /*!
  