Merge branch 'issue/remove-several-warnings' into 'master'

Remove unused-parameter warnings

See merge request iwr/dune-curvedgeometry!11

src/boundaryprojection.cc

@@ -25,7 +25,7 @@ using WorldCoordinate  = FieldVector<double,2>;
 
 int main(int argc, char** argv)
 {
-  MPIHelper& helper = MPIHelper::instance(argc, argv);
+  MPIHelper::instance(argc, argv);
 
   using Grid = YaspGrid<2,EquidistantOffsetCoordinates<double,2>>;
   Grid grid({-1.0,-1.0}, {1.0,1.0}, {20,20});

src/vtkwriter.cc

@@ -21,7 +21,7 @@ const int order = 3;
 int main(int argc, char** argv)
 {
   using namespace Dune;
-  MPIHelper& helper = MPIHelper::instance(argc, argv);
+  MPIHelper::instance(argc, argv);
 
   using Grid = YaspGrid<2>;
   Grid grid({8.0,8.0}, {32,32});