add convenience accessors to is_dynamic_object_exprt

This commit adds two obvious convenience accessors to
is_dynamic_object_exprt.

Author: kroening

src/util/pointer_expr.h

@@ -324,6 +324,16 @@ class is_dynamic_object_exprt : public unary_predicate_exprt
     : unary_predicate_exprt(ID_is_dynamic_object, op)
   {
   }
+
+  exprt &address()
+  {
+    return op();
+  }
+
+  const exprt &address() const
+  {
+    return op();
+  }
 };
 
 template <>