bug#22306: 24.5; Unhide --no-line-directive Documentation

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 10 Jan 2016 00:26:55 +0100
> From: Francesco Potortì <pot@gnu.org>
> Cc: 22306@debbugs.gnu.org, James Muchow <jim_muchow@dell.com>
> 
> >Francesco,
> >
> >Are there any reasons to keep this option (and a few others) hidden
> >from the user eyes?
> 
> For this specific otion, the logs say that I undocumented it in 2002.

My forensic investigation of the history indicates that it was
first introduced in 2002, and undocumented in 2007.

> As far as I can recall, this was because the option seemed too much
> technical to me, that is of little use and difficult to explain.  I
> think I adopted the same criterion for undocumenting the other options.

Well, it seems this option is useful when the original file is no
longer available, which is a legitimate, albeit rare, use case.  So I
un-hided it, and also documented it in etags.1 as the fire-escape in
these rare use cases.

I'm therefore marking this bug done.

Thanks.