with-authinfo-kludge: Change how ssh(1) signals that it's started.

with-authinfo-kludge: Change how ssh(1) signals that it's started.

  * In `server_listen', arrange for the remote shell echo something to
    stdout.  Also, use `read' rather than cat(1), which saves a process
    on the remote system.  And, finally, include a comment so that the
    ps(1) output is approximately useful.

  * In `wait_for_ssh', go into a loop waiting for the echoed stuff from
    the remote servers to arrive (or for them to report early EOF).

Thanks to Ian Jackson for suggesting this approach: it's much better
than the previous one.