FairMQ: Introduce callbacks for the FairMQUnmanagedRegion.

Callbacks are called when the data buffer of the message assiciated
with the corresponding region is no longer needed by the transport.
Example in examples/advanced/Region/

fairmq/shmem/runMonitor.cxx

@@ -0,0 +1,70 @@
+/********************************************************************************
+ *    Copyright (C) 2014 GSI Helmholtzzentrum fuer Schwerionenforschung GmbH    *
+ *                                                                              *
+ *              This software is distributed under the terms of the             *
+ *         GNU Lesser General Public Licence version 3 (LGPL) version 3,        *
+ *                  copied verbatim in the file "LICENSE"                       *
+ ********************************************************************************/
+#include "Monitor.h"
+
+#include <boost/program_options.hpp>
+
+#include <iostream>
+#include <string>
+
+using namespace std;
+using namespace boost::program_options;
+
+int main(int argc, char** argv)
+{
+    try
+    {
+        string segmentName;
+        bool cleanup = false;
+        bool selfDestruct = false;
+        bool interactive = false;
+        unsigned int timeoutInMS;
+
+        options_description desc("Options");
+        desc.add_options()
+            ("segment-name", value<string>(&segmentName)->default_value("fmq_shm_main"), "Name of the shared memory segment")
+            ("cleanup", value<bool>(&cleanup)->implicit_value(true), "Perform cleanup and quit")
+            ("self-destruct", value<bool>(&selfDestruct)->implicit_value(true), "Quit after first closing of the memory")
+            ("interactive", value<bool>(&interactive)->implicit_value(true), "Interactive run")
+            ("timeout", value<unsigned int>(&timeoutInMS)->default_value(5000), "Heartbeat timeout in milliseconds")
+            ("help", "Print help");
+
+        variables_map vm;
+        store(parse_command_line(argc, argv, desc), vm);
+
+        if (vm.count("help"))
+        {
+            cout << "FairMQ Shared Memory Monitor" << endl << desc << endl;
+            return 0;
+        }
+
+        notify(vm);
+
+        if (cleanup)
+        {
+            cout << "Cleaning up \"" << segmentName << "\"..." << endl;
+            fair::mq::shmem::Monitor::Cleanup(segmentName);
+            fair::mq::shmem::Monitor::RemoveQueue("fmq_shm_control_queue");
+            return 0;
+        }
+
+        cout << "Starting monitor for shared memory segment: \"" << segmentName << "\"..." << endl;
+
+        fair::mq::shmem::Monitor monitor{segmentName, selfDestruct, interactive, timeoutInMS};
+
+        monitor.CatchSignals();
+        monitor.Run();
+    }
+    catch (exception& e)
+    {
+        cerr << "Unhandled Exception reached the top of main: " << e.what() << ", application will now exit" << endl;
+        return 2;
+    }
+
+    return 0;
+}