Patch to py3k which adds the "_Py" prefix to the four listed symbols.

With this, the output from "make smelly" is clean (odorless, perhaps?).

However, adding _Py does seem to go against this comment in Include/asdl.h:
/* It would be nice if the code generated by asdl_c.py was completely
   independent of Python, but it is a goal the requires too much work
   at this stage.  So, for example, I'll represent identifiers as
   interned Python strings.
*/