Support MSGTYPE=stop by having qt_display_nhwindow(WIN_MESSAGE,TRUE)
issue a tty-style --More-- prompt. For popup_dialog Off, the prompt
gets appended to the most recent message; for popup_dialog On, it is
issued via a popup and not displayed in the message window.
It accepts <space>, ^J, ^M, and ^[ (ESC) to dismiss. There's no way
to dismiss it with the mouse (for !popup_dialog) which might need
some fix....
Several adventures along the way. The '^C-in-parent-terminal triggers
infinite loop repeatedly complaining about "event loop already running"'
is now a one-shot complaint. It isn't fixed but the severity of
having it happen is greatly reduced.
2e90c1ebd4