Fixed #15852 -- Modified cookie parsing so it can handle duplicate invalid...

Fixed #15852 -- Modified cookie parsing so it can handle duplicate invalid cookie names. Thanks goes to Fredrik Stålnacke for the report and to vung for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16452 bcc190cf-cafb-0310-a4f2-bffc1f526a37