Update libpng to version 1.6.3

Change-Id: I86cb46ec376eb41324b82d2875757aeda734c5c1
diff --git a/updatenotes b/updatenotes
new file mode 100644
index 0000000..9187a0f
--- /dev/null
+++ b/updatenotes
@@ -0,0 +1,12 @@
+Notes for updating libpng in the android tree:
+
+Remove everything, except:
+    pngusr.h
+    Android.mk
+    CleanSpec.mk
+    MODULE_LICENSE_BSD_LIKE
+
+Additionally:
+
+copy the LICENSE file to NOTICE
+copy scripts/pnglibconf.h.prebuilt to pnglibconf.h