Fixed #3604 -- django.contrib.auth password checking now uses hashlib if it's...

Fixed #3604 -- django.contrib.auth password checking now uses hashlib if it's available. Thanks, Rob Hudson

git-svn-id: http://code.djangoproject.com/svn/django/trunk@6318 bcc190cf-cafb-0310-a4f2-bffc1f526a37