This reverts commit 135d20ca.
Conflicts:
	vcl/source/window/window.cxx

There is no implementation of the SystemClipboardExt service, so Window::GetClipboard
would now always fail with catching an Exception, instead of trying to create a
SystemClipboard if SystemClipboardExt is unavailable.  (I'll clean up the unused
SystemClipboardExt in a follow-up commit.)

Change-Id: Ic3c45b148057e174d3487aedb4176549cb28f3c0