Before the change, emacs run in daemon mode without any visible
buffers. Turns out that this affects emacs behavior in some
cases. In particular, `window-end' function returns `point-max'
instead of the last visible position. That makes it hard or
impossible to implement some tests. The patch runs emacs in a
detached screen(1) session. So that it works exactly as if it
has a visible window.
Note: screen terminates when emacs exits. So the patch does not
introduce new "running processes left behind" issues.