[1.0.X] Fixed #9268: pass the "next" param through in the comment preview/post...

[1.0.X] Fixed #9268: pass the "next" param through in the comment preview/post view. Also updated the docs to make this a bit clearer. Backport of r10418 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10419 bcc190cf-cafb-0310-a4f2-bffc1f526a37