Revert r1293: It added little convenience at the cost of extensibility.

IPython/Extensions/ipipe.py

@@ -319,9 +319,6 b' class Table(object):'
     def __iter__(self):
         return xiter(self, "default")
 
-    def __xiter__(self, mode="default"):
-        raise NotImplementedError
-
 
 class Pipe(Table):
     """