remove unused variable.

ok millert@ tedu@

src/lib/libc/string/strnlen.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: strnlen.c,v 1.1 2010/05/18 22:24:55 tedu Exp $	*/
+/*	$OpenBSD: strnlen.c,v 1.2 2010/05/21 06:57:45 chl Exp $	*/
 
 /*
  * Copyright (c) 2010 Todd C. Miller <Todd.Miller@courtesan.com>
@@ -24,7 +24,6 @@ size_t
 strnlen(const char *str, size_t maxlen)
 {
 	const char *cp, *ep;
-	size_t len;
 
 	ep = str + maxlen;
 	for (cp = str; cp < ep && *cp != '\0'; cp++)