[1.2.X] Fixed #15234 -- Ensure that years in a date heirarchy don't use commas...

[1.2.X] 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.

Backport of r15451 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@15455 bcc190cf-cafb-0310-a4f2-bffc1f526a37