Correctly handle MPI_UNSIGNED_LONG.

We incorrectly reference the internal long datatype with the
MPI_UNSIGNED_LONG datatype. Thanks to Kendra Long for finding
and analyzing the issue, as well as for the proposed fix.

Signed-off-by: George Bosilca <[email protected]>

Author: bosilca

ompi/datatype/ompi_datatype_module.c

@@ -374,7 +374,7 @@ const ompi_datatype_t* ompi_datatype_basicDatatypes[OMPI_DATATYPE_MPI_MAX_PREDEF
     [OMPI_DATATYPE_MPI_UB] = &ompi_mpi_ub.dt,
 
     [OMPI_DATATYPE_MPI_LONG] = &ompi_mpi_long.dt,
-    [OMPI_DATATYPE_MPI_UNSIGNED_LONG] = &ompi_mpi_long.dt,
+    [OMPI_DATATYPE_MPI_UNSIGNED_LONG] = &ompi_mpi_unsigned_long.dt,
     /* MPI 3.0 types */
     [OMPI_DATATYPE_MPI_COUNT] = &ompi_mpi_count.dt,