Update multi-part features (nanomsg) and various fixes

- Implement nanomsg multipart with MessagePack.
 - Use the MessagePack from FairSoft and handle not found case.
 - Update splitter, merger and proxy devices to handle multi-part.
 - Let FairMQParts.At() return pointer reference (can be used for moving).
 - Add missing const specifier in the message interface.
 - Add transmit kernel size setting to channels (ZMQ_SNDBUF).
 - Remove FairMQBuffer device.
 - Remove old multi-part methods from Tutorial3 example (to be replaced with Parts API).
 - Make callback mandatory for newMsg(data, size, callback).
 - Add missing <vector> include in FairMQSocket.

fairmq/devices/FairMQBenchmarkSampler.cxx

@@ -35,10 +35,9 @@ FairMQBenchmarkSampler::~FairMQBenchmarkSampler()
 
 void FairMQBenchmarkSampler::Run()
 {
-    void* buffer = malloc(fMsgSize);
     int numSentMsgs = 0;
 
-    unique_ptr<FairMQMessage> baseMsg(fTransportFactory->CreateMessage(buffer, fMsgSize));
+    unique_ptr<FairMQMessage> baseMsg(fTransportFactory->CreateMessage(fMsgSize));
 
     // store the channel reference to avoid traversing the map on every loop iteration
     const FairMQChannel& dataOutChannel = fChannels.at("data-out").at(0);