Fix the signature of _Py_PyAtExit() (GH-3382)
Fix the signature of _Py_PyAtExit() (GH-3382)

Closes #3331.
da-woods/cython,da-woods/cython,cython/cython,scoder/cython,cython/cython,scoder/cython,scoder/cython,cython/cython,scoder/cython,da-woods/cython,da-woods/cython,cython/cython