Use Dune::Vtk::VtkReader from namespace Vtk

amdis/MeshCreator.hpp

@@ -197,7 +197,7 @@ namespace AMDiS
       }
 #if HAVE_DUNE_VTK
       else if (ext == ".vtu") {
-        return Dune::VtkReader<HostGrid, Dune::Vtk::LagrangeGridCreator<HostGrid>>::createGridFromFile(filename);
+        return Dune::Vtk::VtkReader<HostGrid, Dune::Vtk::LagrangeGridCreator<HostGrid>>::createGridFromFile(filename);
       }
 #endif
       else if (ext == ".1d" || ext == ".2d" || ext == ".3d" || ext == ".amc") {