Update config.guess and config.sub. Fixes #550. Fixes #532. Fixes #502.

Per discussion in #248, start writing more CFFI in C instead of Python. This commit gets the individual watcher callbacks into C

Cleanup some warnings in test__doctest.py (an unclosed file, an unknown string escape). Run doctests in a predictable order.

Provide some documentation for gevent.backdoor.BackdoorServer.

c-ares update

Fix Python 3 test failures. Thanks to the contributors of the following issues (at least): Fixes #412. Fixes #413. Fixes #416. Fixes #421. Fixes #462. Fixes #409.

Update the changes from #409 and merge them. Use this new FileObjectPosix to implement the socket._fileobject where possible. Fixes #409.

Better reflect the way leaktests are handled now; this should restore test__backdoor to its FLAKY status on Travis.

Python3 on certain platform (not OS X) raised 'ValueError: cant have unbuffered text I/O', so line buffer it.

Do not support patch_sys under Py3 because of differences in the interpreter that make the current approach using a threadpool unworkable. Fixes test__issue6.

Fix test__example_udp_servers.py by not subclassing _socket.socket, wrapping it instead and providing access to the wrapped socket. This is more like what Python2 does as well.

Fix test__example_echoserver.py. Text/binary issues in the server and client as well as a changed kwarg.

This handles None exception values that would otherwise fail when passed
to traceback.print_exception() and prevent the process from exiting. An associated test is also included.

Fix for issues #461 and #471.