mention that strings in lastlog and utmp are not guaranteed to be NUL-terminated

src/include/utmp.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: utmp.h,v 1.2 1997/09/21 10:46:00 niklas Exp $	*/
+/*	$OpenBSD: utmp.h,v 1.3 1999/04/21 15:15:39 millert Exp $	*/
 /*	$NetBSD: utmp.h,v 1.6 1994/10/26 00:56:40 cgd Exp $	*/
 
 /*
@@ -52,6 +52,11 @@
 #define	UT_LINESIZE	8
 #define	UT_HOSTSIZE	16
 
+/*
+ * Note that these are *not* C strings and thus are not
+ * guaranteed to be NUL-terminated.
+ */
+
 struct lastlog {
 	time_t	ll_time;
 	char	ll_line[UT_LINESIZE];