replace the old declare and don't implement pattern
with C++11 delete keyword
no need to hide this design choice behind access restrictions

Change-Id: I7e8430a07189aa48514a4613c3a8c2950b230f49
Reviewed-on: https://gerrit.libreoffice.org/24495Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>