Made QWindowsCEStyle internal

Made QWindowsCEStyle internal

We will take this opportynity to remove various QStyle specializations
from the public API in Qt5. This gives us much more freedom, for
example changing the inheritance hierarchy, pluginizing etc. without
worrying about BC.

=> Use QStyleFactory and/or QProxyStyle instead of creating an instance
or inheriting QWindowsCEStyle directly.

Change-Id: I6b3c0554e7a2a4a5f0027f4ea1342fd332af89ad
Reviewed-by: Andreas Holzammer <andreas.holzammer@kdab.com>
Reviewed-by: Janne Anttila <janne.anttila@digia.com>