Windows: Fix bug where windows stopped painting after a restore.

Usually, a window get un-exposed when minimized, and exposed
after the first WM_Paint event when restored.

With layered windows (translucent+frameless) we never receive
a WM_Paint, so lets send the expose event when the window is
restired.

Task-number: QTBUG-17548

Change-Id: Ib56d8abd91b15f9238d223fe692b19a3d2c930b7
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
Fix dropshadow and blur graphics effects.

The effects are making assumptions about implementation details of the
paint engine, which had changed between Qt 4 and Qt 5. The engines no
longer implement the pixmap filters and so the assumption made here
was wrong and should be removed.

Task-number: QTBUG-29945
Change-Id: I146d8c8cc12842a323bd613288003afcf89a47c7
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Windows: Fix the code of the native color dialog.

Note: The code is currently #ifdefed out, it is just there
to be able to compare QColorDialog to the native dialog.

Task-number: QTBUG-32054
Change-Id: I042f6701d1a076480cae56c53ae2d3ad303d37d1
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>