also fix DATEVALUE() function that was relying on this dataloss

Change-Id: I6030505a762df3ecbfe9a8331267846d3de817e8
Reviewed-on: https://gerrit.libreoffice.org/17049Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
Tested-by: Michael Meeks <michael.meeks@collabora.com>