Replaced same_drawing_settings() with clone_drawing_settings().

New method is simplier and doesn't use Q3PtrListIterator.
Cleanup: replaced Q3PtrList with QList

Makes code cleaner and nears Qt5 compatibility.
1. foreach used to iterate over lists (except reverse-order iteration);
2. since const T* cannot be attached to QList<T *>, const_cast used in
some places;
3. removed "QString warning;" whenever seen.
Merge pull request #52 from sergey-shambir/q3ptrlist_removal

Q3ptrlist removal