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

[Dmitry Gutov]

On 03/27/2016 06:35 PM, Lars Magne Ingebrigtsen wrote:

> It's less likely that the before/after `M-q' strings hash to the same
> md5 than cosmic rays reprogramming your Emacs into vi, so:

And yet, why would we allow such possibility? String comparison is 
plenty fast already.

Comparing the contents of xdisp.c to itself takes 0.2ms here.

Try:

(setq s (buffer-string))
(setq ss (copy-sequence s))
(benchmark 1 '(equal s ss))