cell values are added in parentheses to make sure negative values are handled
correctly

Change-Id: I7366493e3cd6c25607e311d4b610ef8aa704a8bb
Reviewed-on: https://gerrit.libreoffice.org/19821Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Oliver Specht <oliver.specht@cib.de>
(cherry picked from commit 0bd2a5ee)
Reviewed-on: https://gerrit.libreoffice.org/19826Reviewed-by: Michael Stahl <mstahl@redhat.com>