update file headers with license information (SPDX)
diff --git a/serial/win32.py b/serial/win32.py
index ec380ec..88a1335 100644
--- a/serial/win32.py
+++ b/serial/win32.py
@@ -1,3 +1,9 @@
+#! python
+#
+# (C) 2001-2015 Chris Liechti <cliechti@gmx.net>
+#
+# SPDX-License-Identifier:    BSD-3-Clause
+
 from ctypes import *
 from ctypes.wintypes import HANDLE
 from ctypes.wintypes import BOOL