Problem: Messages preceding a `cmdline_show->prompt` event can not be
distinguished as such when receiving the event. (But since
`msg_show` handlers should be scheduled, one can already check
whether a prompt is active when displaying the message.)
Solution: Rather than add a new kind again, use the `confirm` kind.
Could be seen as slightly misleading where it is more of
a choice rather than a confirmation, but that already applies
to `confirm()` as well...
e16bec41b6
