The empty struct already exists and is called No_Comm (in analogy to MPI_Comm)

[[Imported from SVN: r6094]]

dune/common/mpihelper.hh

@@ -77,7 +77,7 @@ namespace Dune
     /**
      * @brief The type of the mpi communicator.
      */
-    struct MPICommunicator {};
+    typedef No_Comm MPICommunicator;
 
     /**
      * @brief Get the default communicator.