Fix RT memory leak with completion messages found by Ted Moore

A paradigmatic example of why raw pointers are hard: ASyncCmd takes 
ownership of the cmd pointer, but *copies* the completion message (so we 
still need to free the latter)

include/wrapper/Messaging.hpp

@@ -152,8 +152,9 @@ struct FluidSCMessaging{
       args->getb(completionMsgData, completionMsgSize);
     }
     
+    auto ft = getInterfaceTable();
     
-    getInterfaceTable()->fDoAsynchronousCommand(inWorld, replyAddr, getName(), msg,
+    ft->fDoAsynchronousCommand(inWorld, replyAddr, getName(), msg,
         [](World* world, void* data) // NRT thread: invocation
         {
           MessageData* m = static_cast<MessageData*>(data);
@@ -191,6 +192,9 @@ struct FluidSCMessaging{
           delete m;
         },
         static_cast<int>(completionMsgSize), completionMsgData);
+        
+        if(completionMsgSize) ft->fRTFree(inWorld, completionMsgData);
+        
   }
   
   template <size_t N, typename ArgsTuple, size_t... Is> // Call from NRT

include/wrapper/NonRealtime.hpp

@@ -663,6 +663,9 @@ namespace impl {
             args->getb(completionMsgData, completionMsgSize);
           }
           runAsyncCommand(world, cmd, replyAddr, completionMsgSize, completionMsgData);
+          
+          if(completionMsgSize) ft->fRTFree(world, completionMsgData); 
+          
       };
       ft->fDefinePlugInCmd(Command::name(),commandRunner,nullptr);
     }