Add more missing license headers

llvm-svn: 258198
diff --git a/libcxx/utils/sym_check/sym_extract.py b/libcxx/utils/sym_check/sym_extract.py
index 5d89539..a0fbb3e 100755
--- a/libcxx/utils/sym_check/sym_extract.py
+++ b/libcxx/utils/sym_check/sym_extract.py
@@ -1,4 +1,12 @@
 #!/usr/bin/env python
+#===----------------------------------------------------------------------===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is dual licensed under the MIT and the University of Illinois Open
+# Source Licenses. See LICENSE.TXT for details.
+#
+#===----------------------------------------------------------------------===##
 """
 sym_extract - Extract and output a list of symbols from a shared library.
 """