new Networking::DNS category in Bugzilla

So we've now created a Networking::DNS category in bugzilla.

If you should be paying attention to DNS bug traffic, please make sure
to go to Bugzilla | preferences | component watching and add it to
your list of components that you track.

Let's add new DNS bugs to this category (and when you post on existing
DNS bugs, change the category to it).  I suppose we should probably do
a masse switchover at some point, but that will involve lots of spam
(does anyone know of a way to avoid that?).

I suppose in some bookkeeping way it would be good to move fixed DNS
bugs to this category too.  Sigh.

Hopefully this will be a long-term benefit of some kind.  I guess the
takeaway is that it's good to create bugzilla categories for new
things as early as possible...