[1.1.X] Fixed #11711 -- clarified that ValuesQuerySets are not lists per se.

It rarely hurts to think of the returned result from a values() or
values_list() call as a list, but it's really an iterable and sometimes
the difference matters. 

r12743 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12953 bcc190cf-cafb-0310-a4f2-bffc1f526a37