Windows: Adapt custom cursors to observe the system metrics.

Change the cursors Qt provides to use freely scalable pixmap cursors
and scale them to observe system metrics. Make it possible to
use pre-saled bitmap data later by passing the system cursor size
and the intended target size into the creation function
createBitmapCursorFromData().

Task-number: QTBUG-37862
Change-Id: I23899a77f86d0b08b858a81870a57b2e6570ebbe
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>