[Checkins] [zopefoundation/persistent] ce78d9: Don't try to install C headers on PyPy

[Marius Gedminas]

  Branch: refs/heads/fix-pypy-install
  Home:   https://github.com/zopefoundation/persistent
  Commit: ce78d9a10952057742102fe56575ee58536d8fd3
      https://github.com/zopefoundation/persistent/commit/ce78d9a10952057742102fe56575ee58536d8fd3
  Author: Marius Gedminas <marius at gedmin.as>
  Date:   2020-03-06 (Fri, 06 Mar 2020)

  Changed paths:
    M setup.py

  Log Message:
  -----------
  Don't try to install C headers on PyPy

Fixes #135.