QComboBox should remove the last item and insert at top when max count is reached and insertion policy is insertAtTop

In Qt 3 when the maxCount() was reached and the insertionPolicy() was e.g insertAtTop then the last item in the QComboBox would be removed and the new item would be inserted at the top. In Qt 4, the item will not be inserted in this case however, but it should be and the last item should be removed. Similarly, the last item should be removed and the new one inserted for InsertAfterCurrent (unless current is the bottom), InsertBeforeCurrent, and InsertAlphabetically (except when last).