[Cython] PEP draft to get rid of the "cyfunction" class

[Jeroen Demeyer]

I have drafted a PEP (not officially submitted yet) to unify built-in 
and Python functions. Cython could benefit from this because cyfunctions 
could finally be considered functions without sacrificing performance. 
You find the proposal at

https://github.com/jdemeyer/PEP-functions

For comments and discussion, please post on the python-ideas thread
https://mail.python.org/pipermail/python-ideas/2018-March/049563.html


Happy Easter,
Jeroen.