https://ci.appveyor.com/project/denik/gevent/builds/33296254/job/s630snlcgtqmq1fi

Pass addresses through inet_pton before getaddrinfo

The compiler for CPythno2 isn't there on the VS2019 image.

Especially on Windows, that could lead to FDs not being in the expected state. Account for this.

Mainly this is to force Appveyor to run.

It seems that  and  are now mutually exclusive.

The latter can lose information, like IPv6 scope IDs given in the string form.

Add support for Python 3.9

Begin trying to install on Travis.

That breaks several of the subprocess tests.

Catch greenlet.error when destroying a hub from another thread.

Also some test tweaks for OSX on Ci.

Fixes #1631

Fixes #1626

Update c-ares to 1.16.1

Makefile patch doesn't apply, will create a new one.

Update to libuv 1.38

This has new enough kernel headers that libev builds the io_uring
backend, but testing it fails:

  ======================================================================
220  ERROR: test_linux_iouring_0 (gevent.tests.test__close_backend_fd.Test)
221  ----------------------------------------------------------------------
222  Traceback (most recent call last):
223    File "/home/travis/.runtimes/snakepit/2.7.d/lib/python2.7/site-packages/gevent/tests/test__close_backend_fd.py", line 77, in test
224      self._check_backend(backend)
225    File "/home/travis/.runtimes/snakepit/2.7.d/lib/python2.7/site-packages/gevent/tests/test__close_backend_fd.py", line 45, in _check_backend
226      hub = Hub(backend, default=False)
227    File "/home/travis/.runtimes/snakepit/2.7.d/lib/python2.7/site-packages/gevent/hub.py", line 441, in __init__
228      self.loop = self.loop_class(flags=loop, default=default) # pylint:disable=not-callable
229    File "src/gevent/libev/corecext.pyx", line 444, in gevent.libev.corecext.loop.__cinit__
230      raise SystemError("ev_loop_new(%s) failed" % (c_flags, ))
231  SystemError: ev_loop_new(50331776) failed

There are also different SSL errors (of course) on different versions.
gevent.tests.test__makefile_ref.TestSSL commonly fails to find
expected open files on most versions, and some versions don't see the
cipher suites they expect, etc.