Canonicalize single-inclusion macro

dune/solvers/iterationsteps/iterationstep.hh

 // -*- tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 // vi: set et ts=8 sw=4 sts=4:
-#ifndef ITERATIONSTEP_HH
-#define ITERATIONSTEP_HH
+#ifndef DUNE_SOLVERS_ITERATIONSTEPS_ITERATIONSTEP_HH
+#define DUNE_SOLVERS_ITERATIONSTEPS_ITERATIONSTEP_HH
 
 #include <vector>
 #include <string>

dune/solvers/iterationsteps/lineariterationstep.hh

 // -*- tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 // vi: set et ts=8 sw=4 sts=4:
-#ifndef LINEAR_ITERATIONSTEP_HH
-#define LINEAR_ITERATIONSTEP_HH
+#ifndef DUNE_SOLVERS_ITERATIONSTEPS_LINEARITERATIONSTEP_HH
+#define DUNE_SOLVERS_ITERATIONSTEPS_LINEARITERATIONSTEP_HH
 
 #include <memory>
 #include <vector>