test: Skip some flaky tests, but only if they are expected to fail

Task-number: QTBUG-29941
Change-Id: Ieca736c26711fa292855b3281229282628dce608
Reviewed-by: Richard J. Moore <rich@kde.org>
test: Mark tst_QFileSystemWatcher::watchFileAndItsDirectory() as XFAIL

This is a flaky test on Windows 8 64-bit, so marking it as
XFAIL if it is expected to fail.

Task-number: QTBUG-30943
Change-Id: Idd276f80b54fcd5cf295a7e1adebcf0020eaa8ca
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Do not use QWindowsFileDialogHelper for Windows Server 2003

Windows Server 2003 is based on Windows XP and should use
QWindowsXpFileDialogHelper as it does not support the CLSID-based
IFileDialog interfaces that are available from Windows Vista onwards.

Change-Id: Idd973f9ec4c98d1f2fb7e835de64532edeccfc72
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>