xmerge: @Override

Change-Id: I9be006d018335dcbfad5ccba5f55648ba24f609c
Reviewed-on: https://gerrit.libreoffice.org/10577
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>
Tested-by: Noel Grandin <noelgrandin@gmail.com>