[MPIGuard] Add editor hints.

[[Imported from SVN: r6045]]

dune/common/mpiguard.hh

 // -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 // vi: set et ts=4 sw=2 sts=2:
+
 #ifndef DUNE_COMMON_MPIGUARD_HH
 #define DUNE_COMMON_MPIGUARD_HH