fixed (possibly) truncate for GAE

VERSION

@@ -1 +1 @@
-Version 2.4.4-stable+timestamp.2013.03.17.12.10.29
+Version 2.4.4-stable+timestamp.2013.03.17.15.27.04

gluon/dal.py

@@ -4656,7 +4656,7 @@ class GoogleDatastoreAdapter(NoSQLAdapter):
         return self.expand(first)
 
     def truncate(self,table,mode):
-        self.db(table._id).delete()
+        self.db(self.db._adapter.id_query(table)).delete()
 
     def select_raw(self,query,fields=None,attributes=None):
         db = self.db