Bug#206163: /usr/share/man/man8/dselect.8.gz: mention dselect update as the prefered way to keep the available fresh

[Dan Jacobson <jidanni@jidanni.org>]

Package: dselect
Version: 1.10.10
Severity: wishlist
File: /usr/share/man/man8/dselect.8.gz

On the man page, near
       dpkg --update-avail | --merge-avail Packages-file

please mention "dselect update" as being the simple way to keep ones
/var/lib/dpkg/available up to date, as otherwise it would take several
dpkg commands to achieve that.  Also non-dselect users would avoid
reading dselect(8) even though "dselect update" would still be of
value to them.

Also, while we are here, perhaps check the man page for all references
from the days when debian had just one Packages-file, and modernize
them. e.g.,

              in the Packages-file.  The Packages-file distributed
              with Debian is simply named Packages.