Fixed #6505 - Copy plural forms from Django translation files for newly...

Fixed #6505 - Copy plural forms from Django translation files for newly created translation files. Thanks to Ramiro Morales for the initial patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12445 bcc190cf-cafb-0310-a4f2-bffc1f526a37