bug#38384: (next|previous)-buffer silent about not switching

[Eli Zaretskii]

> From: Juanma Barranquero <lekktu@gmail.com>
> Date: Tue, 26 Nov 2019 17:00:35 +0100
> Cc: 38384@debbugs.gnu.org
> 
> After a cursory glance, I find only one instance of (next-buffer) called from 
> elisp in our sources, and it's in
> mode-line-next-buffer.  And in that case, clicking on the buffer name in the 
> modeline and getting a message
> "no next buffer" seems like an improvement to me over the silent treatment ;-)

Granted, I'm worried mainly about code outside of the Emacs tree.