[1.3.X] Fixed #16094: Added clear example of how to refer to custom...

[1.3.X] Fixed #16094: Added clear example of how to refer to custom permissions. Backport of [16813] from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.3.X@16814 bcc190cf-cafb-0310-a4f2-bffc1f526a37