fdo#72645: Case-insensitive string comparison in GETPIVOTDATA.

Change-Id: Ibdb2b7ab2bae03875a3462816e860f58d9076457
Reviewed-on: https://gerrit.libreoffice.org/7285
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>