Defer adjusting the stdlib's list of active threads until threading is monkey-patched

Previously this was done when :mod:`gevent.threading` was imported.
That module is documented to be used as a helper for monkey patching,
so this should generally functionally be the same, but some
applications ignore the directly import that module anyway.

A positive consequence is that ``import gevent.threading, threading;
threading.current_thread()`` will no longer return a DummyThread
before monkey-patching. Another positive consequence is that PyPy will
no longer print a ``KeyError`` on exit if :mod:`gevent.threading` was
imported *without* monkey-patching.

Fixes #984.

Use a weak reference to clean up the link for local objects if they die before the greenlet does (#983)

Fixes #981

In a comment. [skip ci]

If libev is not embedded, we still want to set GEVENT_NO_CFFI_BUILD=1 to
prevent setup.py from trying to configure libev, regardless whether cffi
modules will actually be built or not.

[skip ci]

Commit 59581a8a "Add python 3.5
selectors test, and remove the devpoll selector under 3.5. also update
the monkey documentation." Introduced a regression by moving the exec of
scripts into a main() function. If the script being run with exec has
import statements those are now locally scoped to the main() function
which can break the script.

It does not appear that this local scoping was intentional so the fix is
to exec the script in the global scope, returning the previous behavior.
This also requires setting __package__ = None otherwise the script
appears to be run in the gevent __package__

Instead of singleton instances. This is because exception objects are
stateful on Python 3, so these singletons could potentially be keeping
lots of extra state around.

greenlet.throw() accepts either an instance or a class so this results
in no extra internal changes.

So, raise it directly, instead of trying to use it as a callable.

Use it to fix test_interrupted_write on all Py3, and
test_https_with_cafile on PyPy3.5 instead of disabling them and
patching them inline, respectively.

See #964

* Test PyPy 3.5-5.7.1-beta

Add a missing `clear` method to the tblib Frame object.

[skip appveyor]

* Add PyPy3.5 tests

* Standard PyPy fixes for imported tests.

* more gevent/pypy3.5 blackouts and missing cert files

* another blackballed test due to performance issues.

* missing revocation.crl for test_ssl.py

* Fix test_urllib2_localnet. We had to resort to a patch.

* Adjust timeouts for PyPy3.

* Add test_wsgiref for 3.5 and 3.6 and comment about it being broken

It's broken for all of them, not just PyPy, so move its patch to
reflect that.

Pypy2 5.7.1

This started failing on the newer Ubuntu.

[skip appveyor]

PyPy3-3.5-5.7.1-beta has issues in the traceback
library (https://travis-ci.org/gevent/gevent/jobs/219394025):

  During handling of the above exception, another exception occurred:

  Traceback (most recent call last):
    File "/home/travis/build/gevent/gevent/src/greentest/greentest.py", line 297, in wrap_restore_handle_error
      return method(self, *args, **kwargs)
    File "/home/travis/build/gevent/gevent/src/greentest/greentest.py", line 169, in wrap_timeout
      return method(self, *args, **kwargs)
    File "test__event.py", line 146, in test_set_exception
      self.assertRaises(greentest.ExpectedException, s1.get)
    File "/home/travis/.runtimes/versions/pypy3.5_571/lib-python/3/unittest/case.py", line 728, in assertRaises
      return context.handle('assertRaises', args, kwargs)
    File "/home/travis/.runtimes/versions/pypy3.5_571/lib-python/3/unittest/case.py", line 177, in handle
      callable_obj(*args, **kwargs)
    File "/home/travis/.runtimes/versions/pypy3.5_571/lib-python/3/unittest/case.py", line 201, in __exit__
      traceback.clear_frames(tb)
    File "/home/travis/.runtimes/versions/pypy3.5_571/lib-python/3/traceback.py", line 216, in clear_frames
      tb.tb_frame.clear()
  AttributeError: 'Frame' object has no attribute 'clear'

Fixes #958

[skip appveyor]

Use trusty dist; we seem to be trying to compile pypy for some reason otherwise. Maybe this will fix it. [skip appveyor]

Fix the name of the ``type`` param to gevent.socket.getaddrinfo on Python 3

Previously it would produce a TypeError if a caller tried to pass it
as a keyword argument.

Add a test for this. Also add tests for smtpd under Python 3, which is
where the issue was discovered.

Fixes #960.

Doesn't actually change the license at all, just slightly reformats it. This should be more compatible with github's new license display features.

[skip ci]

Replace optparse with argparse

Fixes #947

Python 2 sockets don't pass type/protocol to getaddrinfo in connect.

Add --quiet option to testrunner.py and use it on CI

Fixes #926

Fixes #943.