Propagate synthesized mouse events in parallel (lock-step) with touch

Propagate synthesized mouse events in parallel (lock-step) with touch

This patch implement the equivalent of
468626e99a90d6ac21cb311cde05c658ccb3b781 in qtdeclarative but for
QtWidgets.

If a widget doesn't accept a touch event, then QApplication gives it
another try by synthesizing a corresponding mouse event. This way
QtQuick and QtWidget behave in a similar way, removing the need for
platform backends to try to emulate a mouse event from a touch event
unconditionally.

Also add relevant unit tests and adjust old QApplication ones.

Change-Id: Iddbf6d756c4b52931a9d1c314b50d7a31dbcdee9
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
Reviewed-by: Kevin Krammer <kevin.krammer@kdab.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>