message: Use modern iterator style, don't use `std::iterator`
  Summary: Reading the email thread from OSS, this seems an easy enough fix for the warning.
diff: @@ -82,17 +82,17 @@ class DexStore {
  boost::optional<size_t> dex_id);
  };
  -class DexStoreClassesIterator
  - : public std::iterator<std::input_iterator_tag, DexClasses> {
  -
  +class DexStoreClassesIterator {
  using classes_iterator = std::vector<DexClasses>::iterator;
  using store_iterator = std::vector<DexStore>::iterator;
  - std::vector<DexStore>& m_stores;
  - store_iterator m_current_store;
  - classes_iterator m_current_classes;
  -
  public:
  + using iterator_category = std::input_iterator_tag;
  + using difference_type = std::ptrdiff_t;
  + using value_type = DexClasses;
  + using pointer = value_type*;
  + using reference = value_type&;
  +
  explicit DexStoreClassesIterator(std::vector<DexStore>& stores)
  : m_stores(stores),
  m_current_store(stores.begin()),
  @@ -139,6 +139,10 @@ class DexStoreClassesIterator
  DexClasses& operator*() { return *m_current_classes; }
  private:
  + std::vector<DexStore>& m_stores;
  + store_iterator m_current_store;
  + classes_iterator m_current_classes;
  +
  void advance_end_classes() {
  while (m_current_store != m_stores.end() &&
  m_current_classes != m_stores.back().get_dexen().end() &&
  