Uamqp

- Fixed seg fault in tearing down a failed link with unsent pending
messages.

- Fixed garbage collection of C objects to prevent crashing on
uncontrolled shutdown.
- Fixed missing event loop references passed into asyncio functions.
- Fixed bug in noneffective flow control when large messages are
received.
- Demote link redirect logging from warning to info.

- Fixed bug in calculating send timeout.
- Removed [ThreadPoolExecutor]{.title-ref} in
[ConnectionAsync]{.title-ref}.
- Added support for Python 3.8

- Fixed bug in dropping received messages at the moment when the
connection just started working.
- Fixed bug where underlying io type wasn\'t set to WebSocket when
http_proxy was applied (PR92, Thanks to skoop22).
- Fixed bug in noneffective timeout when sending messages.
- Added desired-capabilities for [ReceiveClient(Async)]{.title-ref}
and [MessageReceiver(Async)]{.title-ref} as part of the AMQP
protocol.
- Added delivery-tag to [Message]{.title-ref} (azure-sdk-for-python
issue 7336).
- Added method [work]{.title-ref} to [MessageReceiver]{.title-ref} and
[work_async]{.title-ref} to [MessageReceiverAsync]{.title-ref}
responsible for updating link status.

- Made bug fix in asyncio.get_event_loop backwards-compatible for now
by just printing a warning rather than raising an error. In the next
major version bump we can disable entirely.

- Updated the implementation of [update_token()]{.title-ref} in
[JWTTokenAuth]{.title-ref} and [JWTTokenAsync]{.title-ref} (issue
80).