libpng: Upgrade to 1.6.26

This release contains many minor and important fixes.

Libpng 1.6.26 released on October 20, 2016

Change-Id: If647f42a1fb4d7022286010d262d289dac4030df
Signed-off-by: Alex Naidis <alex.naidis@linux.com>
diff --git a/README b/README
index 17bca9a..709c269 100644
--- a/README
+++ b/README
@@ -1,4 +1,4 @@
-README for libpng version 1.6.25 - September 1, 2016 (shared library 16.0)
+README for libpng version 1.6.26 - October 20, 2016 (shared library 16.0)
 See the note about version numbers near the top of png.h
 
 See INSTALL for instructions on how to install libpng.