[1.0.X] Fixed #10016: the cache middleware no longer vomits when handed long...

[1.0.X] Fixed #10016: the cache middleware no longer vomits when handed long URLs. Thanks, Matt Croydon. Backport of r10335 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@10336 bcc190cf-cafb-0310-a4f2-bffc1f526a37