EllisLab/CodeIgniter — pull request #754 by zechdc (2011-12-08 19:51:28+00:00)
Title: Attempted to fix issue #750 -  Upload.php incorrectly detecting mime_typ...

...es for PNG images

- Made the _file_mime_type function fall through a few more checks to make sure it was the proper mime type.
- https://github.com/EllisLab/CodeIgniter/issues/750