Move toward a base type of vector (count, type, blocklen, extent, disp)
with disp and extent applying toward the count repertition and blocklen
being a contiguous memory of type type.
Implement 2 optimizations on this description used during type_commit:
- collapse: successive similar datatype descriptions are collapsed
together with an increased count.
- fusion: fuse successive datatype descriptions in order to minimize the
number of resulting memcpy during pack/unpack.
Fixes at the OMPI datatype level including:
- Fix the create_hindexed and vector creation.
- Fix the handling of [get|set]_elements and _count.
- Correctly compute the dispacement for block indexed types.
- Support the MPI_LB and MPI_UB deprecation, aka. OMPI_ENABLE_MPI1_COMPAT.
Signed-off-by: George Bosilca <bosilca@icl.utk.edu>