instead of yet another private implementation of manual reference
counting

Change-Id: Iefb1d2e595e45a2dfdc3be54e1c51b64afeaf9d8
Reviewed-on: https://gerrit.libreoffice.org/52753Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>