[1.2.X] Fixed #14713 -- documented that resolve can raise Http404. Thanks to...

[1.2.X] Fixed #14713 -- documented that resolve can raise Http404.  Thanks to Adam for the patch. Backport of [14603].

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@14604 bcc190cf-cafb-0310-a4f2-bffc1f526a37