[1.2.X] Fixed #13621 -- Corrected the handling of input formats on date/time...

[1.2.X] Fixed #13621 -- Corrected the handling of input formats on date/time form fields. Thanks to bufke for the report, zerok and jacmkno for their work on the patch, and Karen, Jannis and Alex for feedback.

Backport of r13484 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.2.X@13486 bcc190cf-cafb-0310-a4f2-bffc1f526a37