Feature/mstp zero config option (#564)

* Added a MS/TP zero-config (automatically choose an unused MAC address) using an algorithm that starts with MAC=64 and waits for a random number of PFM (minimum of 8 plus modulo 64) before attempting to choose a MAC sequentially from 64..127. The confirmation uses a 128-bit UUID with the MSTP Test Request frame. The modifications are in src/bacnet/datalink/mstp.c and src/bacnet/datalink/dlmstp.c modules enabling any device to use zero-config if enabled. A working demonstration is in the ports/stm32f4xx for the NUCLEO board. Complete unit testing is included.  Options include lurking forever (wait for a router or another master node before joining) or lurking for a minimum time (enables self forming automatic MAC addressing device nodes).

apps/router/mstpmodule.c

@@ -50,9 +50,7 @@ void *dl_mstp_thread(void *pArgs)
     uint16_t pdu_len;
     uint8_t shutdown = 0;
 
-    shared_port_data.Treply_timeout = 260;
     shared_port_data.MSTP_Packets = 0;
-    shared_port_data.Tusage_timeout = 30;
     shared_port_data.RS485_Handle = -1;
     shared_port_data.RS485_Baud = B38400;
     shared_port_data.RS485MOD = 0;
@@ -95,6 +93,8 @@ void *dl_mstp_thread(void *pArgs)
     if (!dlmstp_init(&mstp_port, port->iface)) {
         printf("MSTP %s init failed. Stop.\n", port->iface);
     }
+    mstp_port.Treply_timeout = 260;
+    mstp_port.Tusage_timeout = 30;
 
     port->port_id = create_msgbox();
     if (port->port_id == INVALID_MSGBOX_ID) {