Also update the 3.5 certificates to something not expired.

Fixes #1692

minor doc fix

Support and require greenlet 0.4.17

The behaviour for ContextVar[cls] changed in some minor patch release of 3.8 and 3.7, and we have too old versions on appveyor.

Fixes #1656

Also disable 32-bit manylinux builds because of https://github.com/cython/cython/issues/3840

Handle SSLEOFError during sock.unwrap() from versions of Python with https://bugs.python.org/issue31122

The unpinned 3.9-dev build caught this.

Fixes #1674

Fix issue 1659

Fixes #1659 and fixes #1661

Memory usage of SSLContext goes down from 416B to 128B after patching.

Fixes #1654

Correct a typo in testing/__init__.py