Use prn0 to show .frogrc settings.

By the time the verbosity level is set, .frogrc has already been read.
Just rename `make-prn` to `define-prn`.
Feed changes:

- Make them pass http://validator.w3.org/feed/

- For the feed stats URI decoration, set utm_source to the tag (such
  as "all" or "some tag") and utm_medium to either RSS or Atom.