Gets rid of the OWriterConnection::createStatement() stub warning. This
is the last interface which was not supported by the writer driver, as
far as I see.

Change-Id: I5d1e6835d30b704d6866f2cc4cd9e82ea0f2139e
Reviewed-on: https://gerrit.libreoffice.org/40134Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>