Message2480

The attached set of patches are an attempt at fixes for
several bugs encountered while executing parts of
test_descr.py from cpython 2.3.5 against jython cvs.

Since test_descr.py is long and many other parts still
fail, i've extracted/simplified the tests of interest
and attached them as a stand-alone script.

The specific bugs are a recursion/stack-overflow in
dict subtypes that override parents __getitem__(),
list's __getslice__()/__setslice__() methods not
accepting the 2/3 argument forms, and an incorrect
error type being raised for certain dict constructor args.

I'm not certain its all correct, review appreciated.

- kz