fix docx redline import (bnc#821804)

This is a squash of commits b6969634..fd26de3b.

Change-Id: I8984001d7f85c00eb9b9943b25b8abb6e2ee28d3
Reviewed-on: https://gerrit.libreoffice.org/11789
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>