Fixed #9268: pass the "next" param through in the comment preview/post view....

Fixed #9268: pass the "next" param through in the comment preview/post view. Also updated the docs to make this a bit clearer.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@10418 bcc190cf-cafb-0310-a4f2-bffc1f526a37