fix a session related prototype in mpi.h

Signed-off-by: Howard Pritchard <hppritcha@gmail.com>

Author: hppritcha

ompi/include/mpi.h.in

@@ -1705,7 +1705,7 @@ OMPI_DECLSPEC  int MPI_Session_create_keyval (MPI_Session_delete_attr_function *
 OMPI_DECLSPEC  int MPI_Session_delete_attr (MPI_Session session, int session_keyval);
 OMPI_DECLSPEC  int MPI_Session_finalize (MPI_Session *session);
 OMPI_DECLSPEC  int MPI_Session_free_keyval(int *session_keyval);
-OMPI_DECLSPEC  int MPI_Session_get_attr (MPI_Session datatype, int session_keyval,
+OMPI_DECLSPEC  int MPI_Session_get_attr (MPI_Session session, int session_keyval,
                                          void *attribute_val, int *flag);
 OMPI_DECLSPEC  int MPI_Session_get_info (MPI_Session session, MPI_Info *info_used);
 OMPI_DECLSPEC  int MPI_Session_get_num_psets (MPI_Session session, int *npset_names);