bug#13949: 24.3.50; `fill-paragraph' should not always put the buffer as modified

[Eli Zaretskii]

> Date: Wed, 13 Mar 2013 23:09:35 +0100
> From: Dani Moncayo <dmoncayo@gmail.com>
> 
> 1. Visit some plain text file.
> 2. Move point to some paragraph with more that one line.
> 3. M-q C-x C-s
> 4. M-q
> 
> After step #3, the buffer is not modified wrt its file (you've just
> save it), but step #4 puts the buffer in a modified state ("**" flag
> in the modeline).
> 
> This seems a bug, since step #4 didn't make any change in the buffer
> contents (the paragraph was already filled).

Step #4 does change the buffer, because M-q doesn't know whether the
paragraph is already filled, so it fills it anew each time.

Emacs always behaved like that.