[Cython] Py3k builds broken due to CPython changes

[Stefan Behnel]

Hi,

just a quick heads-up that the Py3k builds are completely broken since this
week-end because the internal CPython import mechanism changed. The most
visible effect for us is that Py2-style imports no longer work in Py3.3,
which, I guess, impacts the majority of existing Py2-style Cython code.
Only absolute and relative imports continue to work, import level "-1"
raises a ValueError.

I asked on python-dev to see what they think about this regression.

http://thread.gmane.org/gmane.comp.python.devel/131858/focus=131909

If they end up considering it the intended behaviour, we may have to
duplicate the original behaviour in one way or another to keep this working.

Stefan