give rhs constructor parameter the const qualifier - same as in the

setter method as well as the base clas constructors

dune/solvers/iterationsteps/multigridstep.hh

@@ -34,7 +34,7 @@
 
         MultigridStep(const MatrixType& mat,
                       VectorType& x,
-                      VectorType& rhs,
+                      const VectorType& rhs,
                       int mu, int nu1, int nu2,
                       LinearIterationStep<MatrixType, VectorType>* preSmoother,
                       LinearIterationStep<MatrixType, VectorType>* postSmoother,
@@ -56,7 +56,7 @@
 
         MultigridStep(const MatrixType& mat,
                       VectorType& x,
-                      VectorType& rhs) :
+                      const VectorType& rhs) :
             LinearIterationStep<MatrixType, VectorType>(mat, x, rhs),
             basesolver_(0),
             preprocessCalled(false)