Included <cassert> to prevent compile time error

[[Imported from SVN: r1248]]

common/genericiterator.hh

@@ -5,6 +5,7 @@
 #define DUNE_GENERICITERATOR_HH
 
 #include <dune/common/iteratorfacades.hh>
+#include <cassert>
 
 namespace Dune
 {

grid/sgrid.hh

@@ -224,6 +224,8 @@ namespace Dune {
   public:
     SBoundaryEntity() : elem_(true) {}
 
+    int id () const { return -1; }
+
     //! return true if ghost cell was calced
     bool hasGeometry () { return false; };