Merge bugfixes done in Gnus trunk

Merge bugfixes done in Gnus trunk

Those changes fix only the bugs having appeared in the bug list.
Many other Gnus changes not yet merged to Emacs are in:
   ftp://ftp.jpl.org/pub/tmp/MaGnus-to-Emacs.patch
(or http://www.jpl.org/ftp/pub/tmp/MaGnus-to-Emacs.patch)

2012-06-10 Lars Magne Ingebrigtsen <larsi@gnus.org>
* gnus-group.el (gnus-group-get-new-news): Respect
  `gnus-group-use-permanent-levels', as documented (bug#11638).
2012-06-10 Dave Abrahams <dave@boostpro.com>
* gnus-int.el (gnus-warp-to-article): Limit registry warping to real
  groups (bug#11641).