Missing string.h include.

Index: xlito.c
--- xlito.c.orig
+++ xlito.c
@@ -1,6 +1,7 @@
 #include <fcntl.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <ctype.h>
 #include <errno.h>
 #include "ddxli.h"