Fix a dim/dimworld mixup

This patch is needed to make the code compile when dim!=dimworld.

dune/fufem/prolongboundarypatch.hh

@@ -55,7 +55,7 @@ public:
                     const int dim      = GridType::dimension;
                     const int dimworld = GridType::dimensionworld;
                     typedef typename GridType::ctype ctype;
-                    FieldVector<ctype,dimworld-1> dummy;
+                    FieldVector<ctype,dim-1> dummy;
                     FieldVector<ctype,dimworld> level0Normal = i.unitOuterNormal(dummy);
 
                     // Find all boundary segments of the descendants of this element