[Release][GMRES] don't copy the Krylov basis in the update method

The full krylov basis is copied in the call of the method update(),
working with a reference to the krylov basis reduced the peak amount of allocated memory
by a factor of about 1.7 and improves the runtime by 4%.

Steffen: Also constified all applicable function arguments as suggested
         by Christian.

Closes FS#1378

dune/istl/solvers.hh

@@ -1301,8 +1301,8 @@ namespace Dune {
 
     static void
     update(X &x, int k,
-           std::vector< std::vector<field_type> > & h,
-           std::vector<field_type> & s, std::vector<F> v)
+           const std::vector< std::vector<field_type> > & h,
+           const std::vector<field_type> & s, const std::vector<F> &v)
     {
       std::vector<field_type> y(s);