updated a bunch of headers

for the new license

lib/common/compiler.h

@@ -1,3 +1,12 @@
+/*
+ * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under both the BSD-style license (found in the
+ * LICENSE file in the root directory of this source tree) and the GPLv2 (found
+ * in the COPYING file in the root directory of this source tree).
+ */
+
 #ifndef ZSTD_COMPILER_H
 #define ZSTD_COMPILER_H