FPII-2034: DO NOT MERGE Update libpng to 1.6.20

DO NOT MERGE Update libpng to 1.6.20

BUG:23265085
Change-Id: I2fc2106965c789a54f04412e9c63a0901b0c1e71
(cherry picked from commit 0b39f202aaedd3029e4270d2af7d58ba6634f9cd)
diff --git a/scripts/def.c b/scripts/def.c
new file mode 100644
index 0000000..c3e424d
--- /dev/null
+++ b/scripts/def.c
@@ -0,0 +1,29 @@
+/* def.c - define format of libpng.def
+ *
+ * Last changed in libpng version 1.6.16 [December 22, 2014]
+ * Copyright (c) 2011-2014 Glenn Randers-Pehrson
+ *
+ * This code is released under the libpng license.
+ * For conditions of distribution and use, see the disclaimer
+ * and license in png.h
+ */
+
+/* Write the export file header: */
+PNG_DFN ";--------------------------------------------------------------"
+PNG_DFN "; LIBPNG module definition file for OS/2"
+PNG_DFN ";--------------------------------------------------------------"
+PNG_DFN ""
+PNG_DFN "; If you give the library an explicit name one or other files"
+PNG_DFN "; may need modifying to support the new name on one or more"
+PNG_DFN "; systems."
+PNG_DFN "LIBRARY"
+PNG_DFN "OS2 DESCRIPTION "PNG image compression library""
+PNG_DFN "OS2 CODE PRELOAD MOVEABLE DISCARDABLE"
+PNG_DFN ""
+PNG_DFN "EXPORTS"
+PNG_DFN ";Version 1.6.20"
+
+#define PNG_EXPORTA(ordinal, type, name, args, attributes)\
+        PNG_DFN "@" SYMBOL_PREFIX "@@" name "@"
+
+#include "../png.h"