update mqttd program, add buzzer control and test ok

Guo Wenxue

2019-08-03 415fe8988e579c3185c7ba074733859506c1c7c3

 apue/1.File_IO/ds18b20.c

@@ -116,5 +116,7 @@
    /* convert string value to float value */
    *temp = atof(ptr)/1000;
   
    close(fd);

    return 0;
}