Fix shebang on python scripts

Signed-off-by: falkTX <falktx@gmail.com>

utils/png2c.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # DISTRHO Plugin Framework (DPF)

utils/png2rgba.py

@@ -1,8 +1,8 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 # DISTRHO Plugin Framework (DPF)
-# Copyright (C) 2012-2016 Filipe Coelho <falktx@falktx.com>
+# Copyright (C) 2012-2019 Filipe Coelho <falktx@falktx.com>
 #
 # Permission to use, copy, modify, and/or distribute this software for any purpose with
 # or without fee is hereby granted, provided that the above copyright notice and this