Windows: Use new clipboard API for listening to changes.

The currently used clipboard chain API has various problems with non-
responsive applications and requires checks for hung/debugged applications when
sending on notifications.

The new clipboard format listener API available from Windows Vista onwards
requires less code and does not have these problems, however the change
notifications now arrive asynchronously.

Change the tst_qclipboard  to be able to deal with asynchronous change
notifications.

Task-number: QTBUG-38670
Task-number: QTBUG-33492
Change-Id: I3c49e346a34310431c20f3051d12eaabf330a3ad
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>