Update libpng from 1.6.3 to 1.6.10

Change-Id: I76e81e7fd267d15991cd342c5caeb2fe77964ebf
diff --git a/png.5 b/png.5
index eaefa29..3beacfa 100644
--- a/png.5
+++ b/png.5
@@ -1,4 +1,4 @@
-.TH PNG 5 "July 18, 2013"
+.TH PNG 5 "March 6, 2014"
 .SH NAME
 png \- Portable Network Graphics (PNG) format
 .SH DESCRIPTION