8074662: Update 3rd party readme and license for LibPNG v 1.6.16

Reviewed-by: jeff

THIRD_PARTY_README

@@ -1250,7 +1250,7 @@ included with JDK 8 and OpenJDK 8 source distributions.
 
 -------------------------------------------------------------------------------
 
-%% This notice is provided with respect to libpng 1.5.4, which may be 
+%% This notice is provided with respect to libpng 1.6.16, which may be
 included with JRE 8, JDK 8, and OpenJDK 8.
 
 --- begin of LICENSE ---
@@ -1266,8 +1266,8 @@ this sentence.
 
 This code is released under the libpng license.
 
-libpng versions 1.2.6, August 15, 2004, through 1.5.4, July 7, 2011, are
-Copyright (c) 2004, 2006-2011 Glenn Randers-Pehrson, and are
+libpng versions 1.2.6, August 15, 2004, through 1.6.16, December 22, 2014, are
+Copyright (c) 2004, 2006-2014 Glenn Randers-Pehrson, and are
 distributed according to the same disclaimer and license as libpng-1.2.5
 with the following individual added to the list of Contributing Authors
 
@@ -1364,7 +1364,7 @@ certification mark of the Open Source Initiative.
 
 Glenn Randers-Pehrson
 glennrp at users.sourceforge.net
-July 7, 2011
+December 22, 2014
 
 --- end of LICENSE ---