setModel on the header(s) of a QAbstractItemView leads to a memory leak

For example for a QTreeView (but is the same for other item views like QTableView)

=============src\gui\itemviews\qtreeview.cpp, Line 235, QTreeView::setModel(..):=============
d->header->setModel(model);
QAbstractItemView::setModel(model);

=============src\gui\itemviews\qheader.cpp, Line 410, QHeaderView::setModel(..):=============
QAbstractItemView::setModel(model);

=============src\gui\itemviews\qabstractitemview.cpp, Line 682, QAbstractItemView::setModel(..):=============
setSelectionModel(new QItemSelectionModel(d->model, this));

But you in qtreeview.cpp we also have:

=============src\gui\itemviews\qtreeview.cpp, Line 277, QTreeView::setSelectionModel(..):=============
d->header->setSelectionModel(selectionModel);
=================================

So we are creating 2 QItemSelectionModel for the header: one from the header setModel and one from the QTreeView::setSelectionModel. The first one is never used and never deleted.

A patch is included to work around the memory leak.