[dune-pdelab] Clang and stokesdg_vecfem.hh

[Christoph Grüninger]

Hi PDELabers,
I need this patch to make headerchecks work for PDELab with Clang. I'd 
like it, if you appy it.

Greets
Christoph

--- dune/pdelab/localoperator/stokesdg_vecfem.hh        (revision 2221)
+++ dune/pdelab/localoperator/stokesdg_vecfem.hh        (working copy)
@@ -579,9 +579,9 @@
        static void add_compute_flux(const M & du, const R & n, R & result)
        {
          const int N = du.N();
-        const int M = du.M();
+        const int M_ = du.M();
          for(int r=0; r<N; ++r)
-          for(int c=0; c<M; ++c)
+          for(int c=0; c<M_; ++c)
              result[r] += du[r][c] * n[c];
        }