Fixed 16938 -- Ensured that the active locale's formats take precedence over...

Fixed 16938 -- Ensured that the active locale's formats take precedence over the default settings even if they would be interpreted as False in a conditional test (e.g. 0 or empty string). Thanks to pikerr for the report and initial patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17017 bcc190cf-cafb-0310-a4f2-bffc1f526a37