title: Eclipse paho mqtt C++ as dependency in another project
body: <p>I have not much clue how c and c++ works at compile and runtime!</p>
  
  <p>We are trying to use Eclipse Paho C++ library as a dependency in the project and messed up right now.</p>
  
  <p>We have reffered to <a href="https://github.com/eclipse/paho.mqtt.cpp/tree/master/src/samples" rel="nofollow">https://github.com/eclipse/paho.mqtt.cpp/tree/master/src/samples</a> and used the same code in our project but we get this error.</p>
  
  <blockquote>
    <p>error: 'mqtt' has not been declared class callback : public virtual mqtt::callback</p>
  </blockquote>
  
  <p>We also have the following in place </p>
  
  <ol>
  <li>Copied all the C and C++ libs(libmqttpp.so  libpaho-mqtt3a.so.1.0   libpaho-mqtt3c.so.1  libmqttpp.so.0       libpaho-mqtt3as.so      libpaho-mqtt3c.so.1.0 libmqttpp.so.0.1     libpaho-mqtt3as.so.1    libpaho-mqtt3cs.solibpaho-mqtt3a.so    libpaho-mqtt3as.so.1.0  libpaho-mqtt3cs.so.1
  libpaho-mqtt3a.so.1  libpaho-mqtt3c.so       libpaho-mqtt3cs.so.1.0) to /usr/local/lib</li>
  <li>Copied .h files(MQTTAsync.h  MQTTClient.h  MQTTClientPersistence.h) to /usr/local/include</li>
  </ol>
  
  <p>Apart from above 2 steps, do I need to add anything to my project to resolve the problem or I am missing anything.</p>