use the DUNE version of static_assert to support older compilers.

[[Imported from SVN: r6377]]

dune/common/fvector.hh

@@ -92,7 +92,7 @@ namespace Dune {
     template<class K1, int SIZE1>
     explicit FieldVector (const FieldVector<K1,SIZE1> & x)
     {
-      static_assert(SIZE1 == SIZE, "FieldVector in costructor has wrong size");
+      dune_static_assert(SIZE1 == SIZE, "FieldVector in costructor has wrong size");
       for (size_type i = 0; i<SIZE; i++)
         _data[i] = x[i];
     }