hdf5_msb

[svn-r4772] Purpose:
    Bug Fix.

Description:
    Equation to compute size of attribute in memory was incorrectly using the
    disk's datatype (and dataspace, but that turns out not to have been the
    actual issue) and when a variable length datatype was used for the
    attribute, the wrong size is being computed.

    Also, the variable-length datatype conversions aren't handling the
    default dataset transfer property list (H5P_DEFAULT) correctly.

Solution:
    Changed attribute code to compute the attribute size in memory correctly
    by using the memory datatype & dataspace.

    Changed the variable-length datatype conversion code to use the default
    dataset transfer property list when H5P_DEFAULT is passed as the property
    list ID.

Platforms tested:
    FreeBSD 4.5 (sleipnir)