Fixed #14750 -- ILPostalCodeField didn't handle all EMPTY_VALUES correctly. ...

Fixed #14750 -- ILPostalCodeField didn't handle all EMPTY_VALUES correctly.  Also converted the Israeli localflavor testcases to use the new, less verbose format.  Thanks to Idan Gazit.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14943 bcc190cf-cafb-0310-a4f2-bffc1f526a37