fixed a bunch of headers after license change (#825)
diff --git a/lib/common/threading.c b/lib/common/threading.c
index 141376c..4e47b6b 100644
--- a/lib/common/threading.c
+++ b/lib/common/threading.c
@@ -2,9 +2,9 @@
  * Copyright (c) 2016 Tino Reichardt
  * All rights reserved.
  *
- * This source code is licensed under the BSD-style license found in the
- * LICENSE file in the root directory of this source tree. An additional grant
- * of patent rights can be found in the PATENTS file in the same directory.
+ * 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).
  *
  * You can contact the author at:
  * - zstdmt source repository: https://github.com/mcmilk/zstdmt
@@ -15,9 +15,9 @@
  */
 
 /* When ZSTD_MULTITHREAD is not defined, this file would become an empty translation unit.
-* Include some ISO C header code to prevent this and portably avoid related warnings.
-* (Visual C++: C4206 / GCC: -Wpedantic / Clang: -Wempty-translation-unit)
-*/
+ * Include some ISO C header code to prevent this and portably avoid related warnings.
+ * (Visual C++: C4206 / GCC: -Wpedantic / Clang: -Wempty-translation-unit)
+ */
 #include <stddef.h>