Keeping control this way simplifies and unifies the implementations.

- Fix a concurrency bug in FileObjectPosix that we were hiding with buffering and a RuntimeError.
- Add all the error checking the stdlib does, with a few exceptions that make sense.

See #1441.

And add tests.

Fixes #1441.

Update Python versions, including 3.8 final on Appveyor

Fix pylint 2.4 new warnings.

Attempting to match Python 3.8 fixes in subprocess.py, especially on Windows.

Attempting to fix psutil-related regression in PyPy 7.2

corrected a typo in comments

* Fix tests with TLS1.3

There were hidden assumptions about the order in which greenlets would run.

TLS1.3 changed the handshake in a way that broke those assumptions.

* Attempting to fix the appveyor backdoor test timeouts.

Suspect a buffering issue. Trying to fix by disabling Nagle's algorithm.

Also a cleaner separation of concerns in the backdoor server.

* Brute-force debugging.

* Tweak the backlog and simultaneous accept settings, and drop the extra event listeners we don't need.

* max_accept=1 and dropping the events fixed test__backdoor on windows.

probably it was just the events. test that.

* Brute force debugging for the SSL issues.

* Some of the windows ssl issues may be due to fileno reuse and hence incorrectly multiplexed watchers?

* Even more care with socket lifetimes.

On Python 3.7, use the newer wrapping form that the stdlib uses to create the _sslobj.

* More debugging.

* The preferred method of unwrapping differs on 3.6 and 3.7+

* Checking ordering.

* Partial success, hopefully.

* Lots of progress. Try again.

* More Windows work.

* D'oh. Test cases from 3.7.4 handle some of these issues more gracefully so we will just use them.

* Tweaks.

* Having a hard time getting 3.7 updated on Travis. Try to force the issue.

* Yet another weird error from appveyor.

Add support for Python 3.8b4

Still needs the specific networking test classes added, but all the basics pass for me. Lets see about CI.

Dynamic class in gevent.resolver.thread.Resolver.__repr__

Fix references to six.PY3 in case python4 becomes a thing

monkey: allow to execute a module rather than only a script

API docs: remove duplicated entries for gevent.{queue,server}

Fixes: b7c9a1df ("Reorganize docs.")