hdf5_ep

[svn-r5260] Purpose:
    Code cleanup

Description:
    Previously, the I/O pipeline (pline), external file list (efl) and fill-
    value (fill) structs were passed down the raw data function call chain,
    even into and/or through functions which didn't use them.  Since all three
    of these pieces of information are available from the dataset creation
    property list, just pass the dataset creation property list down the
    function call chain and query for the information needed in a particular
    function.

Platforms tested:
    FreeBSD 4.5 (sleipnir)