Upgraded PNG library from 1.5.5 to 1.5.7

nickgammon · nickgammon · commit aa5415a13eab · 2011-12-22T12:47:59.000+11:00
diff --git a/png/readme.txt b/png/readme.txt
@@ -2,7 +2,7 @@ PNG built as follows:
 
 1. Download recent version from download.sourceforge.net
 
-    In this case: lpng155.zip
+    In this case: lpng157.zip
 
 2. Uncompress the archive with 7-Zip (if necessary), obtainable from:
 
