bug#51377: Automatically exit server when it has no remaining clients

[Gregory Heytings]

> I'm not sure I understand the patch; `save-buffers-kill-emacs' prompts 
> the user to save buffers before killing Emacs, but how would that work 
> in a daemon when there are no frames remaining?

There is one (invisible) frame remaining: the daemon frame.  And when 
there are no other frames (graphical or non-graphical) ones, there's 
nothing to save, save-buffer-kill-emacs just kills emacs.  The patch just 
checks every two seconds if there are remaining frames (apart from the 
daemon one), and if not, it kills emacs.  And it works with and without 
-n.