iscsi-scst: Fix recently introduced compiler warnings

Fix the following two compiler warnings:

chap.c: In function 'chap_rand':
chap.c:347:5: warning: implicit declaration of function 'read' [-Wimplicit-function-declaration]
chap.c:348:5: warning: implicit declaration of function 'close' [-Wimplicit-function-declaration]


git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@4623 d57e44dd-8a1f-0410-8b47-8ef2f437770f

iscsi-scst/usr/chap.c

@@ -29,6 +29,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <fcntl.h>
+#include <unistd.h>
 #include "sha1.h"
 #include "md5.h"