I don't think your patch applies cleanly:
<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>404 Not Found</title> </head><body> <h1>Not Found</h1> <p>The requested URL /~iwamatsu/libpng/patches/exactimage_0.8.5-1.patch was not found on this server.</p> <hr> <address>Apache Server at people.debian.org Port 80</address> </body></html>
:P -- Jakub Wilk