Co-authored-by: Antti Haapala <antti.haapala@anttipatterns.com>

* Fix AttributeError (not all SSL exceptions have 'errno' attribute)

* Increase default handshake timeout from 10 to 60 seconds
* Make sure start_tls can be cancelled correctly
* Make sure any error in SSLProtocol gets propagated (instead of just being logged)

This reverts commit 5d97b7bc.

Original patch by Dan O'Reilly.

* Also in docs

* bpo-32662: Implement Server.start_serving() and Server.serve_forever()

New methods:

* Server.start_serving(),
* Server.serve_forever(), and
* Server.is_serving().

Add 'start_serving' keyword parameter to loop.create_server() and
loop.create_unix_server().

* Add abstract get_loop() method to Server, AbstractServer classes.
* Add test cases for get_loop() method in Server, AbstractServer classes
* Add documentation for get_loop() method

* Make ssh_handshake_timeout None by default.
* Raise ValueError if ssl_handshake_timeout is used without ssl.
* Raise ValueError if ssl_handshake_timeout is not positive.

10 seconds by default.

* Implement functionality
* Add documentation

asyncio.get_event_loop(), and, subsequently asyncio._get_running_loop()
are one of the most frequently executed functions in asyncio.  They also
can't be sped up by third-party event loops like uvloop.

When implemented in C they become 4x faster.

* Convert asyncio/tasks.py to async/await

* Convert asyncio/queues.py to async/await

* Convert asyncio/test_utils.py to async/await

* Convert asyncio/base_subprocess.py to async/await

* Convert asyncio/subprocess.py to async/await

* Convert asyncio/streams.py to async/await

* Fix comments

* Convert asyncio/locks.py to async/await

* Convert asyncio.sleep to async def

* Add a comment

* Add missing news

* Convert stubs from AbstrctEventLoop to async functions

* Convert subprocess_shell/subprocess_exec

* Convert connect_read_pipe/connect_write_pip to async/await syntax

* Convert create_datagram_endpoint

* Convert create_unix_server/create_unix_connection

* Get rid of old style coroutines in unix_events.py

* Convert selector_events.py to async/await

* Convert wait_closed and create_connection

* Drop redundant line

* Convert base_events.py

* Code cleanup

* Drop redundant comments

* Fix indentation

* Add explicit tests for compatibility between old and new coroutines

* Convert windows event loop to use async/await

* Fix double awaiting of async function

* Convert asyncio/locks.py

* Improve docstring

* Convert tests to async/await

* Convert more tests

* Convert more tests

* Convert more tests

* Convert tests

* Improve test

* bpo-31970: Reduce performance overhead of asyncio debug mode.

* bpo-31819: Add AbstractEventLoop.sock_recv_into()

* Add NEWS

* Add doc

* call remove_done_callback in finally section

* Optimize get_event_loop and _get_running_loop

* rename _loop_pid as loop_pid and add blurb news

* rename _loop_pid as loop_pid and add blurb news

* add back _RunningLoop

* Update 2017-09-05-10-30-48.bpo-31350.dXJ-7N.rst

* Update 2017-09-05-10-30-48.bpo-31350.dXJ-7N.rst

when called from coroutines or callbacks.

Run expensive type checks only in debug mode.  In addition, stop
supporting passing handles to loop.run_in_executor.

Patch by iceboy.