we trade off a little accuracy for finding more possible write-only
fields.

Change-Id: I9f7edba99481fe4ded0a9d8e45e911b0ee99d269
Reviewed-on: https://gerrit.libreoffice.org/56715
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>