Merge branch 'issue/float128' into 'master'

make an explicit cast to field type for shape-function values

See merge request spraetor/dune-vtk!29

dune/vtk/gridcreators/lagrangegridcreator.hh

@@ -324,9 +324,11 @@ namespace Dune
         localBasis.evaluateFunction(x, shapeValues_);
         assert(shapeValues_.size() == localNodes_.size());
 
+        using field_type = typename LocalBasisTraits::RangeType::field_type;
+
         GlobalCoordinate out(0);
         for (std::size_t i = 0; i < shapeValues_.size(); ++i)
-          out.axpy(shapeValues_[i], localNodes_[i]);
+          out.axpy(field_type(shapeValues_[i]), localNodes_[i]);
 
         return out;
       }