Fixed #3594 - Added ability to discard the language catalog in the JavaScript i18n view in case the selected language is English but no English translation catalog actual exists, e.g. due to being the language translated from. Thanks to msaelices, aryx and Ramiro Morales.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12384 bcc190cf-cafb-0310-a4f2-bffc1f526a37