py-cython: updated to 0.29.18

0.29.18

Bugs fixed
* Exception position reporting could run into race conditions on threaded code.
  It now uses function-local variables again.
* Error handling early in the module init code could lead to a crash.
* Error handling in ``cython.array`` creation was improved to avoid calling
  C-API functions with an error held.
* A memory corruption was fixed when garbage collection was triggered during calls
  to ``PyType_Ready()`` of extension type subclasses.
* Memory view slicing generated unused error handling code which could negatively
  impact the C compiler optimisations for parallel OpenMP code etc.  Also, it is
  now helped by static branch hints.
* Cython's built-in OpenMP functions were not translated inside of call arguments.
* Complex buffer item types of structs of arrays could fail to validate.
* Decorators were not allowed on nested `async def` functions.
* C-tuples could use invalid C struct casting.
* Optimised ``%d`` string formatting into f-strings failed on float values.
* Optimised aligned string formatting (``%05s``, ``%-5s``) failed.
* When importing the old Cython ``build_ext`` integration with distutils, the
  additional command line arguments leaked into the regular command.
* When using the ``CYTHON_NO_PYINIT_EXPORT`` option in C++, the module init function
  was not declared as ``extern "C"``.
* Three missing timedelta access macros were added in ``cpython.datetime``.


(adam)