Patch from Gnus' trunk is attached.  Major changes are listed below.

* Changed pgg-gpg-decrypt-region to write out an encrypted armor to a
file.  This should fix the problem Sacsha reported.

* Added new interface function pgg-list-keys.  This function returns
more information about keys than pgg-lookup-key.  For example:

  (pgg-list-keys "ueno")
  =>
  (((pub (trust . "u") (length . 1024) (algorithm . 17)
         (key-id . "A5B6B2D4B15813FE") (creation-date . "1002618643")
         (expiration-date . "1155189267") (ownertrust . "u")
         (capability . "scESC"))
    (uid (trust . "u") (creation-date . "1060581267")
         (hash . "461300972A811B7CDF6EE9ED3E918AD940E4F384")
         (user-id . "Daiki Ueno <ueno@unixuser.org>"))))

* Added some notes in comments/docstrings of backend functions to
prevent direct usage.

* pgg-gpg-recipient-argument is abolished, because "-r" has the same
meaning as "--remote-user" and "--recipient".