Make state updates and rendering event driven

The main thing preventing this system being event driven in the past was
input from the keyboard had to be polled separately from pty activity.
This commit adds a thread for the window event iterator and sends them
on the same channel as pty characters.

With that in place, the render loop looks like

    - Block on 1 available input
    - Get all remaining available input that won't cause blocking
    - Render

Which means that rendering is only performed on state changes. This
obsoleted the need for a `dirty` flag in the Term struct.

0 files changed, 0 insertions, 0 deletions