This commit extracts out the IOLoop functions which are used to define an
IOLoop that send and receive messages on Jupyter channels into is own object.
* jupyter-channel-ioloop.el: New file.
(jupyter-channel-ioloop): A sub-type of `jupyter-ioloop` that sets up an IOLoop
to send/receive messages on Jupyter channels.
(jupyter-ioloop-channels):
(jupyter-ioloop-session): New variables used in `jupyter-channel-ioloop`
events.
(jupyter-ioloop-add-arg-type jupyter-channel): Moved from `jupyter-client.el`.
(jupyter-channel-ioloop-add-session): New function.
(jupyter-ioloop-start): Setup ioloop to communicate with Jupyter channels.
(jupyter-channel-ioloop-recv-messages):
(jupyter-channel-ioloop-add-start-channel-event):
(jupyter-channel-ioloop-add-stop-channel-event):
(jupyter-channel-ioloop-add-send-event): Moved from `jupyter-client.el`,
replaced jupyter-ioloop prefix with jupyter-channel-ioloop.
* jupyter-client.el: Require `jupyter-channel-ioloop` instead of
`jupyter-ioloop`.
(jupyter-kernel-client): Change type of `ioloop` to `jupyter-channel-ioloop`.
(jupyter-client--ioloop-setup-form): Remove.
(jupyter-ioloop-add-arg-type jupyter-channel): Move to
`jupyter-channel-ioloop.el`.
(jupyter-ioloop-add-start-channel-event):
(jupyter-ioloop-add-stop-channel-event):
(jupyter-ioloop-add-send-event): Move to `jupyter-channel-ioloop.el`, replace
jupyter-ioloop prefix with jupyter-channel-ioloop.
(jupyter-ioloop-start): Remove.
(jupyter-start-channels): Ensure `jupyter-ioloop-start` method of
`jupyter-channel-ioloop` is called. Set ioloop process buffer to `-buffer` slot
of client.
* jupyter-ioloop.el (jupyter-ioloop-start): Remove :before method.
