Fix (static) buffer overflow bug. The dest buffer is of size MAXPATHLEN,

so dest[MAXPATHLEN] falls outside the buffer.  This bug corrupted
arenas[0] defined in libc's malloc.c on PowerPC when kldxref is shared,
which triggered a delayed SIGSERV.

usr.sbin/kldxref/kldxref.c

@@ -260,7 +260,7 @@ maketempfile(char *dest, const char *root)
 	int fd;
 
 	strncpy(dest, root, MAXPATHLEN - 1);
-	dest[MAXPATHLEN] = '\0';
+	dest[MAXPATHLEN-1] = '\0';
 
 	if ((p = strrchr(dest, '/')) != 0)
 		p++;