Windows: Add platform plugin parameter for tablet absolute range.

Make the range for detecting relative (mouse mode) configureable
using  -platform windows:tabletabsoluterange=50

Task-number: QTBUG-36937

Change-Id: I44f928e53cb41b246c44554ec7f71bfbdf03c147
Reviewed-by: Arthur Krebsbach <Arthur.Krebsbach@Wacom.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Windows: Set source of synthesized mouse events correctly.

The source was never set for OS-synthesized events, causing duplicated
touch clicks to occur in Quick 2 applications.

Task-number: QTBUG-31386

Change-Id: Ib6d1405815dfb8e57d6446c72a7d6e2a044281ea
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Widgets: Pass on mouse event source when translating mouse events.

Change-Id: I70dacc2f96552e08dd71d5cbd63fb4cf9916c11f
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>