$NetBSD: patch-ab,v 1.4 2012/02/04 21:57:54 shattered Exp $

Fix build with png-1.5.

--- tools/pngio.h.orig	2010-10-27 12:41:49.000000000 +0000
+++ tools/pngio.h
@@ -21,6 +21,7 @@
 #define PNGIO_H
 
 #include <png.h>
+#include <zlib.h>
 
 typedef struct
 {  char *name;
