Problem: Extui does not route messages emitted as a result of a typed
command to the "more" window.
Command message leading shell messages is missing a kind.
Messages not routed to 'cmdheight' area after it was 0.
Solution: Route messages that were emitted in the same event loop as an
entered command to the "more" window. Also append multiple
messages in an already open more-window.
Assign it the `shell_cmd` kind.
Change message position when 'cmdheight' changes from 0.
7e787f6a4f