Fixed #15234 -- Ensure that years in a date heirarchy don't use commas for...

Fixed #15234 -- Ensure that years in a date heirarchy don't use commas for thousand separators, regardless of the value of USE_THOUSAND_SEPARATOR. Thanks to Julien Phalip for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15451 bcc190cf-cafb-0310-a4f2-bffc1f526a37