more licensing

include/libc.h

@@ -1,3 +1,7 @@
+// This file originated as Plan 9's /sys/include/libc.h.
+// The plan9port-specific changes may be distributed
+// using the license in ../src/lib9/LICENSE.
+
 /*
  * Lib9 is miscellany from the Plan 9 C library that doesn't
  * fit into libutf or into libfmt, but is still missing from traditional

include/u.h

@@ -1,3 +1,5 @@
+// See ../src/lib9/LICENSE
+
 #ifndef _U_H_
 #define _U_H_ 1
 #if defined(__cplusplus)

src/lib9/LICENSE

@@ -4,6 +4,8 @@ terms of the simpler MIT-style license at the bottom of this file.
 The files listed below were written from scrach for plan9port
 and do not derive from the Plan 9 from Bell Labs distribution.
 
+	../../include/u.h
+	non-Plan 9 code in ../../include/libc.h
 	_exits.c
 	_p9dialparse.c
 	_p9dir.c