Subclasses of QStyledItemDelegate cannot get correct behaviour from superclass paint()

Add a custom delegate to a styled view such as a QTreeWidget. If the custom delegate paint method passes its parameters on to QStyledItemDelegate.paint we would expect the original paint behaviour. In fact, we get a non-styled version of paint and cannot access the original styled painting action other than by recreating from scratch.

Example included creates a QTreeWidget and adds a delegate to column 1. The delegate does nothing - it just forwards paints to the superclass. But it messes up the highlighting on column 1. The superclass call behaves like QItemDelegate instead of QStyledItemDelegate.

I don't know why this happens but it may be related to the bug in PySide-115.