bug#13801: [PATCH] Trivial fix for files.el

[Chong Yidong]

Xue Fuqiao <xfq.free@gmail.com> writes:

> I made a minor patch for files.el.  The patch does this:
>
> 1. Improve the doc string for `break-hardlink-on-save';

Thanks, I committed a slightly different fix.

> 2. Remove an unnecessary `buffer-auto-save-file-name'.
>
> -                            buffer-auto-save-file-name
>                              (file-readable-p buffer-auto-save-file-name)

This is not unnecessary.  If buffer-auto-save-file-name is nil, the next
line would signal an error, which is undesireable.