BUG/MEDIUM: lua/socket: Buffer error, may segfault

The buffer pointer is already updated. It is again updated
when it is given to the function ci_putblk().

This patch must be backported in 1.6, 1.7 and 1.8

src/hlua.c

@@ -1974,7 +1974,7 @@ static int hlua_socket_write_yield(struct lua_State *L,int status, lua_KContext
 	/* send data */
 	if (len < send_len)
 		send_len = len;
-	len = ci_putblk(&s->req, buf+sent, send_len);
+	len = ci_putblk(&s->req, buf, send_len);
 
 	/* "Not enough space" (-1), "Buffer too little to contain
 	 * the data" (-2) are not expected because the available length