The index method is not complete, and returns 0 with
comments of FIXME.
This patch causes the index method to return a Python
list of strings representing the indices of the object.
(Note: I've not done much Python C programming, so
please check the reference counting semantics; I've
patterned it after other code in snmpymodule.c, and it
appears to work, but there may be subtleties about
which I am unaware.)