This does sort the main problem of screen.Fini(), but really we
want to use a separate Pause() and Resume() function, because
screen.Fini() is not meant for reuse in this way.
Note that one side effect of this change is that applications which
redirect stdin and stdout and expect us to just use /dev/tty instead
are going to break -- we are now using stdin and stdout like nearly
every other screen oriented application.