Add new function called UNIQUE to the function list.
(TODO: dynamic array in separate patch, oasis proposal)
Change-Id: Ie138aee545995d4af1e66be5a4cf4e99e6e2f581
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/167484
Tested-by: Jenkins
Reviewed-by: Balazs Varga <balazs.varga.extern@allotropia.de>