- compare iteratorBase == iteratorBase by value, not position
  thus this works
      list[a] == list[b] ...

- compare iterator == iteratorBase and const_iterator == iteratorBase
  by position, not value. The inheritance rules means that this works:
      iter == list.end() ...
  this will compare positions:
      iter == list[5];
  Of course, this will still compare values:
      *iter == list[5];