Upgrade libpng to 1.2.44 for security fixes.

Change-Id: Iae257ca6ea7031a99f38e9de196d71ef8b94f9aa
diff --git a/scripts/makefile.darwin b/scripts/makefile.darwin
index 7e28127..ed7a8e3 100644
--- a/scripts/makefile.darwin
+++ b/scripts/makefile.darwin
@@ -4,7 +4,7 @@
 # derived from makefile.linux:
 #  Copyright (C) 1998, 1999 Greg Roelofs
 #  Copyright (C) 1996, 1997 Andreas Dilger
-
+#
 # This code is released under the libpng license.
 # For conditions of distribution and use, see the disclaimer
 # and license in png.h
@@ -22,7 +22,7 @@
 # Library name:
 LIBNAME = libpng12
 PNGMAJ = 12
-PNGMIN = 1.2.38
+PNGMIN = 1.2.44
 PNGVER = $(PNGMAJ).$(PNGMIN)
 
 # Shared library names: