Updating libutf to a newer version.

This brings us in sync with the google3 //third_party/utf
implementation.

Change-Id: I0f3e013304bab6d609ddf0b2619f3b5b8ec6f047
diff --git a/runestrcmp.c b/runestrcmp.c
index a368613..c274625 100644
--- a/runestrcmp.c
+++ b/runestrcmp.c
@@ -7,17 +7,17 @@
  * or modification of this software and in all copies of the supporting
  * documentation for such software.
  * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
- * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE
- * ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
+ * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR LUCENT TECHNOLOGIES MAKE ANY
+ * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
  * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
  */
 #include <stdarg.h>
 #include <string.h>
-#include "plan9.h"
 #include "utf.h"
+#include "utfdef.h"
 
 int
-runestrcmp(Rune *s1, Rune *s2)
+runestrcmp(const Rune *s1, const Rune *s2)
 {
 	Rune c1, c2;