hdf5_ep

[svn-r7468] Purpose:
    Code cleanup, etc.

Description:
    Generalize Ray's datatype fixes to handle packing compound datatypes which
are the base type of an array or variable-length type, etc.

    Also track "packedness" of a compound datatype from it's creation, instead
of only setting the 'packed' flag after the datatype was explicitly packed.

    Updated docs to reflect that a compound datatype is allowed to grow (but
not shrink).

Platforms tested:
    FreeBSD 4.9 (sleipnir)
    h5committest