py-cython: updated to 0.29.6

0.29.6:

Bugs fixed

* Fix a crash when accessing the __kwdefaults__ special attribute of
  fused functions.

* Fix the parsing of buffer format strings that contain numeric sizes, which
  could lead to incorrect input rejections.

* Avoid a C #pragma in old gcc versions that was only added in GCC 4.6.
  Patch by Michael Anselmi.

* Auto-encoding of Unicode strings to UTF-8 C/C++ strings failed in Python 3,
  even though the default encoding there is UTF-8.

(adam)