message: Add struct keyword in front of internal_iterator
diff: @@ -8089,8 +8089,8 @@ class basic_json
  iter_impl& operator=(iter_impl<basic_json> other) noexcept(
  std::is_nothrow_move_constructible<pointer>::value and
  std::is_nothrow_move_assignable<pointer>::value and
  - std::is_nothrow_move_constructible<internal_iterator>::value and
  - std::is_nothrow_move_assignable<internal_iterator>::value
  + std::is_nothrow_move_constructible<struct internal_iterator>::value and
  + std::is_nothrow_move_assignable<struct internal_iterator>::value
  )
  {
  std::swap(m_object, other.m_object);
  @@ -8107,8 +8107,8 @@ class basic_json
  iter_impl<const basic_json>& operator=(iter_impl<const basic_json> other) noexcept(
  std::is_nothrow_move_constructible<pointer>::value and
  std::is_nothrow_move_assignable<pointer>::value and
  - std::is_nothrow_move_constructible<internal_iterator>::value and
  - std::is_nothrow_move_assignable<internal_iterator>::value
  + std::is_nothrow_move_constructible<struct internal_iterator>::value and
  + std::is_nothrow_move_assignable<struct internal_iterator>::value
  )
  {
  std::swap(m_object, other.m_object);
  @@ -8601,7 +8601,7 @@ class basic_json
  /// associated JSON instance
  pointer m_object = nullptr;
  /// the actual iterator of the associated instance
  - internal_iterator m_it = internal_iterator();
  + struct internal_iterator m_it = internal_iterator();
  };
  /*!
  