mod_mime_magic fails to identify PNG (Portable Network Graphics) images because
the stock magic file contains no description of the PNG format.

How to reproduce:

1. Build Apache with --enable-mime-magic.
2. Make sure MIMEMagicFile is set correctly in httpd.conf (it should be correct
in a default installation).
3. Put a PNG file somewhere in the document tree and give it a name without a
.png suffix.
4. Request the PNG file using a tool that allows you to view the HTTP response
headers, such as "wget -S".
5. Examine the Content-Type header.  Using the stock magic file, the type should
match the server's DefaultType setting (text/plain unless changed).

How to fix:

Add a description of the PNG format to the magic file.  This appears to work:

0       string          \x89PNG
>4      belong          0x0d0a1a0a      image/png

The PNG specification can be found at http://www.w3.org/TR/PNG

Thanks.