message: mpidummy: proper size in snprintf
  Fix buffer size and warning
  "could not gather data" directive output truncated writing
  22 bytes into a region of size 5 [-Wformat-truncation]
diff: @@ -170,7 +170,8 @@ int MPI_Gather(const void *sendbuf, int sendcnt, MPI_Datatype sendtype,
  }
  else
  {
  - std::snprintf(mpierrmsg, ier, "could not gather data\n");
  + std::snprintf(mpierrmsg, MPI_MAX_ERROR_STRING,
  + "could not gather data\n");
  }
  return ier;
  @@ -247,7 +248,8 @@ int MPI_Scatter(const void *sendbuf, int sendcnt, MPI_Datatype sendtype,
  }
  else
  {
  - std::snprintf(mpierrmsg, ier, "could not scatter data\n");
  + std::snprintf(mpierrmsg, MPI_MAX_ERROR_STRING,
  + "could not scatter data\n");
  }
  return ier;
  