message: Fix - multiindex operator++ was not incrementing this
diff: @@ -209,12 +209,16 @@ class multi_index
  const T& operator*()const { return *static_cast<const T*>(_item); }
  const T* operator->()const { return static_cast<const T*>(_item); }
  - const_iterator operator++(int)const {
  - return ++(const_iterator(*this));
  + const_iterator operator++(int){
  + const_iterator result(*this);
  + ++(*this);
  + return result;
  }
  - const_iterator operator--(int)const {
  - return --(const_iterator(*this));
  + const_iterator operator--(int){
  + const_iterator result(*this);
  + --(*this);
  + return result;
  }
  const_iterator& operator++() {
  @@ -503,11 +507,16 @@ class multi_index
  const T& operator*()const { return *static_cast<const T*>(_item); }
  const T* operator->()const { return static_cast<const T*>(_item); }
  - const_iterator operator++(int)const {
  - return ++(const_iterator(*this));
  + const_iterator operator++(int) {
  + const_iterator result(*this);
  + ++(*this);
  + return result;
  }
  - const_iterator operator--(int)const {
  - return --(const_iterator(*this));
  +
  + const_iterator operator--(int) {
  + const_iterator result(*this);
  + --(*this);
  + return result;
  }
  const_iterator& operator++() {
  