rename some variables to distinguish them from type name
use enumarray for log level strings
remove unused DATA member

Change-Id: Id3c38b82e679b3aede5ce790735443e769d5f236
Reviewed-on: https://gerrit.libreoffice.org/28920Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>
Tested-by: Noel Grandin <noel.grandin@collabora.co.uk>