Update tblib version for pytest compatibility

Hopefully this is why the build stages aren't running for https://travis-ci.org/github/gevent/gevent/builds/660126948?utm_medium=notification&utm_source=github_status (#1541)

Correct a typo in patched_tests_setup.py

Remove the deprecated magic proxy gevent.signal.

Leave behind the actual module gevent.signal, and the callable gevent.signal_handler.

Fixes #1596

Rework the way the in-place patcher works.

It now handles multiple imports better and doesn't pollute the namespace of an original module object if it happened to be pre-imported.

Fixes #1526

Packaging updates: use common_utility_include_dir for Cython, and don…

Packaging updates: use common_utility_include_dir for Cython, and don't install/include generated .c/.h files in wheels

docs/api/gevent.rst: fix typo

Refactor test__all__ to make it easier to spot errors. PyPy 7.2 on Windows has a failure with it; this won't fix it but is the first step. Make PyPy on windows non-optional so we catch such failures easier.

Fixes #1466

Add extra tests around selectors.

Fixes #1461 (hopefully).

Add greenlet-local implementation of contextvars

Include traceback in threadpool logging. Hoping to find where test__subprocess_interrupted is failing on Py2

These are greenlet local.

Fixes #1407

Fix Popen.communicate() to raise exceptions from reading the streams. 

And a general clean up of how the streams are read, ensuring we just have one greenlet. This avoids the 'reentrant call' errors that could prevent closing the streams on time.

Fixes #1510

The two-arg version of super depends on a module global, making it flaky during interpreter shutdown. Seen on Python 2: https://travis-ci.org/gevent/gevent/jobs/636366809#L501

Also some cleanups to subprocess handling during tests. Avoid a ref cycle.