start mqtt client (based on paho.mqtt.c), basically works

3rd/paho.mqtt.c/src/MQTTExportDeclarations.h

@@ -0,0 +1,36 @@
+/*******************************************************************************
+ * Copyright (c) 2020, 2020 Andreas Walter
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * and Eclipse Distribution License v1.0 which accompany this distribution.
+ *
+ * The Eclipse Public License is available at
+ *    https://www.eclipse.org/legal/epl-2.0/
+ * and the Eclipse Distribution License is available at
+ *   http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * Contributors:
+ *    Andreas Walter - initially moved export declarations into separate fle
+ *******************************************************************************/
+
+#if !defined(EXPORTDECLARATIONS_H)
+#define EXPORTDECLARATIONS_H
+
+#if defined(_WIN32)
+#   if defined(PAHO_MQTT_EXPORTS)
+#       define LIBMQTT_API __declspec(dllexport)
+#   elif defined(PAHO_MQTT_IMPORTS)
+#       define LIBMQTT_API __declspec(dllimport)
+#   else
+#       define LIBMQTT_API
+#   endif
+#else
+#    if defined(PAHO_MQTT_EXPORTS)
+#       define LIBMQTT_API  __attribute__ ((visibility ("default")))
+#    else
+#       define LIBMQTT_API extern
+#    endif
+#endif
+
+#endif