[Python-3000] Ordered mapping type for Python 3000?

["Martin v. Löwis"]

> I believe the reason for immutable *args is one of optimization.

I think there is also a correctness issue at work. For an immutable
argument tuple, you can be sure that the tuple won't change "behind
you". That, in turn, means that PyArg_ParseTuple can return borrowed
references, so that C functions don't have to decref the arguments
the have fetched. If the argument tuple was mutable, that would
be much more risky.

Regards,
Martin