Sync some handler fixes and demo object fixes and updates and some comment fixes from branch bacnet-stack-0-8-0.

bacnet-stack/demo/handler/h_cov.c

@@ -892,13 +892,13 @@ void handler_cov_subscribe(
     bytes_sent =
         datalink_send_pdu(src, &npdu_data, &Handler_Transmit_Buffer[0],
         pdu_len);
+    if (bytes_sent <= 0) {
 #if PRINT_ENABLED
-    if (bytes_sent <= 0)
         fprintf(stderr, "SubscribeCOV: Failed to send PDU (%s)!\n",
             strerror(errno));
-#else
-    bytes_sent = bytes_sent;
 #endif
+    }
+
 
     return;
 }