[libpng16] bump version to 1.6.0beta04
diff --git a/pngconf.h b/pngconf.h
index 426d42a..b545dce 100644
--- a/pngconf.h
+++ b/pngconf.h
@@ -1,7 +1,7 @@
 
 /* pngconf.h - machine configurable file for libpng
  *
- * libpng version 1.6.0beta03 - December 22, 2011
+ * libpng version 1.6.0beta04 - December 22, 2011
  *
  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)