[1.3.x] Fixed #15496 -- Corrected handling of base64 file upload encoding....

[1.3.x] Fixed #15496 -- Corrected handling of base64 file upload encoding. Backport of r16176 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.3.X@17546 bcc190cf-cafb-0310-a4f2-bffc1f526a37