bug#13949: 24.4.1; `fill-paragraph' should not always put the buffer as modified

[Eli Zaretskii]

> From: Lars Magne Ingebrigtsen <larsi@gnus.org>
> Date: Mon, 28 Mar 2016 13:27:49 +0200
> 
> I've now made a simple buffer hashing function (that does not take text
> properties into account) to see how slow this would be.
> 
> The following form
> 
> (with-temp-buffer
>   (dotimes (i 10000)
>     (insert (make-string 100 ?k) "\n"))
>   (benchmark-run 1000 (buffer-hash)))
> 
> takes 2.7 seconds (that's 1000 1MB buffers), and unsurprisingly
> 
> (with-temp-buffer
>   (dotimes (i 10000000)
>     (insert (make-string 100 ?k) "\n"))
>   (benchmark-run 1 (progn (message "%s" (buffer-size) (buffer-hash)))))
> 
> (which is 1 1GB buffer) takes the same amount of time.  :-)
> 
> (This is on a 2.7GHz i5 from like five years ago.)

Optimized build or unoptimized?