Fixed the BACnet/IP broadcast messages to send as BVLC_ORIGINAL_BROADCAST_NPDU. Corrected comments about Broadcasts.

bacnet-stack/ports/pic18f6720/dlmstp.c

@@ -315,7 +315,7 @@ void dlmstp_get_broadcast_address(BACNET_ADDRESS * dest)
         dest->mac_len = 1;
         dest->mac[0] = MSTP_BROADCAST_ADDRESS;
         dest->net = BACNET_BROADCAST_NETWORK;
-        dest->len = 0;          /* len=0 denotes broadcast address  */
+        dest->len = 0; /* always zero when DNET is broadcast */
         for (i = 0; i < MAX_MAC_LEN; i++) {
             dest->adr[i] = 0;
         }