Update libpng to version 1.6.3

Change-Id: I86cb46ec376eb41324b82d2875757aeda734c5c1
diff --git a/png.5 b/png.5
index 20b584e..eaefa29 100644
--- a/png.5
+++ b/png.5
@@ -1,4 +1,4 @@
-.TH PNG 5 "July 9, 2011"
+.TH PNG 5 "July 18, 2013"
 .SH NAME
 png \- Portable Network Graphics (PNG) format
 .SH DESCRIPTION
@@ -18,7 +18,7 @@
 platforms.
 
 .SH "SEE ALSO"
-.IR libpng(3) ", " zlib(3) ", " deflate(5) ", and " zlib(5)
+.BR "libpng"(3), " libpngpf"(3), " zlib"(3), " deflate"(5), " " and " zlib"(5)
 .LP
 PNG specification (second edition), November 2003:
 .IP
@@ -35,7 +35,7 @@
 RFC 2083
 .IP
 .br
-ftp://ftp.rfc-editor.org:/in-notes/rfc2083.txt
+ftp://ds.internic.net/rfc/rfc2083.txt
 .br
 or (as a W3C Recommendation) at
 .br