Windows: Restore maximized/full screen widgets to correct screen.

Windows: Restore maximized/full screen widgets to correct screen.

Partially revert 54865d47cfd859a0e84ba8e1bbff3b56c93d4e0d and
bring back parts from abba37cd0eff959edf2d011842cbf2b36cce8467 which
failed some tests on other platforms and never made it in.

Avoid setting a geometry on maximized windows since that leaves
them in a broken state. Instead, if there is a need to restore
maximized windows to a different screen, clear the maximized flag
before applying the geometry.

[ChangeLog][QWidget][Windows] QWidget::restoreGeometry() now restores
maximized/full screen widgets to the correct screen.

Task-number: QTBUG-21371
Task-number: QTBUG-4397

Change-Id: Ibd5b736e921f20d4b7365c06c6f9c5dd4469c781
Reviewed-by: Andy Shaw <andy.shaw@digia.com>
(cherry picked from qtbase/ae4243df1e53b0aaeada708f6fa7979a0f0d216a)