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

Set EV_USE_REALTIME, EV_USE_MONOTONIC and EV_USE_FLOOR.

Fixes #1648

https://travis-ci.org/github/gevent/gevent/jobs/700121977

PyPy is failing with https://travis-ci.org/github/gevent/gevent/jobs/699973435

pip is now emitting a warning on appveyor, which appears to break powershell installing twine, and hence uploads.

Add libuv linked sources for Cygwin builds.  Fixes #1578

Relax the psutil version pin for PyPy.

5.7.0 works on Linux, but it still won't build on Windows.

Fixes #1643

Make selectors2 truly optional on Py2 with dnspython

Fixes #1641

Fix docstrings for the derived classes needed to get atomic semaphore behaviour in pure-python mode.

Fixes #1639

This should save a minute or so.

Run on Ubuntu Bionic

On Ubuntu Bionic in CI, we see the system resolver return fewer results than our other resolvers, so just require a matching subset.

Also drop libev's verification level. Static asserts that crash the process ARE NOT HELPFUL.