bug#29420: 26.0; doc of `list-packages'

[Eli Zaretskii]

> Date: Thu, 23 Nov 2017 18:05:57 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> 
> `C-h f list-packages' should give you a better description of the
> display that results.  It wouldn't hurt to succinctly describe each
> column.

I added the list of columns.

> `C-h r g package menu' should give you a better description.  It should
> describe each column of the display.

It does that already.

> It could describe column `status' better, for instance.  Apparently
> one of the possible values is `dependency', but that is not
> mentioned.

Patches to improve the documentation of package.el in the manual are
most welcome.  I generally find its documentation inadequate and
outdated, and tried to improve that as best I could, but I don't know
enough about it to do a better job, and apparently (and sadly) no one
else is interested.

Thanks.