Add an `AUTHORS` file and update copyright notices.

Change-Id: Ifb505e5664996c1af41e38376e58ba49864213a3
diff --git a/tools/test.py b/tools/test.py
index 5445191..8bfd2c2 100755
--- a/tools/test.py
+++ b/tools/test.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python2.7
 
-# Copyright 2015, ARM Limited
+# Copyright 2015, VIXL authors
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without