...instead of using the current mouse position. This
is important if event processing is delayed: we want
the QMouseEvent to have the position when the event
happened, not the current position.

Regression from Qt 4.

Change-Id: Ifd4f0f02853236a204de96c5a97e72f86c29f0b7
Task-id: QTBUG-37926
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@theqtcompany.com>