also removing an odd Swap function in sw::util::Setlayer

Change-Id: Ied4a4bb5a6ef3f6bdd29c40b19680600536407bc
Reviewed-on: https://gerrit.libreoffice.org/45740Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>