license: Update copyright
-Copyright (c) 2010 - 2019, Alfred E. Heggestad
-Copyright (c) 2010 - 2019, Richard Aas
-Copyright (c) 2010 - 2019, Creytiv.com
+Copyright (C) 2020 - 2021, Baresip Foundation (https://github.com/baresip)
+Copyright (c) 2010 - 2021, Alfred E. Heggestad
+Copyright (c) 2010 - 2020, Richard Aas
+Copyright (c) 2010 - 2020, Creytiv.com
All rights reserved.
