Add an `AUTHORS` file and update copyright notices.

Change-Id: Ifb505e5664996c1af41e38376e58ba49864213a3
diff --git a/src/code-buffer-vixl.cc b/src/code-buffer-vixl.cc
index 522f939..d2f14f5 100644
--- a/src/code-buffer-vixl.cc
+++ b/src/code-buffer-vixl.cc
@@ -1,4 +1,4 @@
-// Copyright 2014, ARM Limited
+// Copyright 2014, VIXL authors
 // All rights reserved.
 //
 // Redistribution and use in source and binary forms, with or without