py-cython: updated to 0.29.16

0.29.16:

Bugs fixed
* Temporary internal variables in nested prange loops could leak into other
  threads.
* Default arguments on fused functions could crash.
* C-tuples declared in ``.pxd`` files could generate incomplete C code.
* Fused functions were not always detected and optimised as Cython
  implemented functions.
* Valid Python object concatenation of (iterable) strings to non-strings
  could fail with an exception.
* Using C functions as temporary values lead to invalid C code.
* Fix an unhandled C++ exception in comparisons.
* Fix deprecated import of "imp" module.
* Fix compatibility with Pythran 0.9.6 and later.
* The ``_Py_PyAtExit()`` function in ``cpython.pylifecycle`` was misdeclared.
* Several missing declarations in ``cpython.*`` were added.
* A declaration for ``libc.math.fpclassify()`` was added.
* Avoid "undeclared" warning about automatically generated pickle methods.
* Avoid C compiler warning about unreachable code in ``prange()``.
* Some C compiler warnings in PyPy were resolved.

(adam)