vchoi_fork

[svn-r5680] Purpose:
    New feature.

Description:
    There is some discussion among the SAF team as to whether it is better
    to use MPI derived types for raw data transfers (thus needing a
    MPI_File_set_view() call), or whether it is better to use a sequence of
    low-level MPI types (i.e. MPI_BYTE) for the raw data transfer.

Solution:
    Added an in internal flag to determine whether derived types are preferred
    (the default), or whether they should be avoided.  An environment variable
    ("HDF5_MPI_PREFER_DERIVED_TYPES") can be set by users to control whether MPI
    types should be used or not.  Set the environment variable to "0" (i.e.:
    'setenv HDF5_MPI_PREFER_DERIVED_TYPES 0' to avoid using MPI derived types.

Platforms tested:
    IRIX64 6.5 (modi4) w/parallel