Adjust include guards to Dune style

dune/solvers/common/boxconstraint.hh

 // -*- tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 // vi: set et ts=8 sw=4 sts=4:
-#ifndef DUNE_BOX_CONSTRAINT_HH
-#define DUNE_BOX_CONSTRAINT_HH
+#ifndef DUNE_SOLVERS_COMMON_BOX_CONSTRAINT_HH
+#define DUNE_SOLVERS_COMMON_BOX_CONSTRAINT_HH
 
 #include <array>
 #include <limits>