fdo#84938: replace MIB_ constants with enum

Change-Id: I58c1b4c9e4c4b3751b233d2fe10b9c953b945c4a
Reviewed-on: https://gerrit.libreoffice.org/12179
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>