[dynamic polymorphism] Add dynamic category to SuperLU

dune/istl/superlu.hh

@@ -283,6 +283,13 @@ namespace Dune
     typedef Dune::BlockVector<
         FieldVector<T,n>,
         typename A::template rebind<FieldVector<T,n> >::other> range_type;
+
+    //! Category of the solver (see SolverCategory::Category)
+    virtual SolverCategory::Category category() const
+    {
+      return SolverCategory::Category::sequential;
+    }
+
     /**
      * @brief Constructs the SuperLU solver.
      *