Canonicalize single-inclusion macro

dune/grid/common/defaultgridview.hh

 // -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 // vi: set et ts=4 sw=2 sts=2:
-#ifndef DUNE_DEFAULTGRIDVIEW_HH
-#define DUNE_DEFAULTGRIDVIEW_HH
+#ifndef DUNE_GRID_COMMON_DEFAULTGRIDVIEW_HH
+#define DUNE_GRID_COMMON_DEFAULTGRIDVIEW_HH
 
 #include <dune/common/typetraits.hh>
 #include <dune/common/exceptions.hh>