Fixed #13444 -- Improved the documentation around the backwards compatibility...

Fixed #13444 -- Improved the documentation around the backwards compatibility quirks of the cycle and include tags. Thanks to awmcclain for the report.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13063 bcc190cf-cafb-0310-a4f2-bffc1f526a37