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).

src/bacnet/datalink/mstptext.c

@@ -87,3 +87,18 @@ const char *mstptext_frame_type(unsigned index)
     return indtext_by_index_split_default(mstp_frame_type_text, index,
         FRAME_TYPE_PROPRIETARY_MIN, "UNKNOWN", "PROPRIETARY");
 }
+
+static INDTEXT_DATA mstp_zero_config_state_text[] = { 
+    { MSTP_ZERO_CONFIG_STATE_INIT, "INIT" },
+    { MSTP_ZERO_CONFIG_STATE_IDLE, "IDLE" },
+    { MSTP_ZERO_CONFIG_STATE_LURK, "LURK" },
+    { MSTP_ZERO_CONFIG_STATE_CLAIM, "CLAIM" },
+    { MSTP_ZERO_CONFIG_STATE_CONFIRM, "CONFIRM" },
+    { MSTP_ZERO_CONFIG_STATE_USE, "USE" },
+    { 0, NULL } 
+ };
+
+const char *mstptext_zero_config_state(unsigned index)
+{
+    return indtext_by_index_default(mstp_zero_config_state_text, index, "unknown");
+}