From: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
Subject: Fix FTBFS with libpng 1.5

--- a/src/pngSave.cpp
+++ b/src/pngSave.cpp
@@ -19,7 +19,7 @@
  
 #include "progress.h"
 
-typedef Byte byte;
+typedef unsigned char byte;
 
 
 void downsample2x2(byte * data, int sx, int sy){