+ don't write string ref syntax if it hasn't been read or explicitly
changed

Change-Id: Id3788a71a4a3d0672283a4770c7d7a9608beb06f
Reviewed-on: https://gerrit.libreoffice.org/17326Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>