vchoi_fork

[svn-r12592] Description:
    Several changes, all mooshed together:
        - Add support for "tiny" objects - which can be stored in the heap
            ID itself, instead of in the heap data blocks.
        - Flesh out support for compressed direct blocks, but comment it
            out until John's got some metadata cache changes in place to
            support it.
        - Add support for applying I/O pipeline filters to 'huge' objects
        - Refactor 'huge' object code to store information for 'huge' objects
            directly in the heap ID, when there are I/O pipeline filters
            applied to the heap (and the heap ID is large enough to hold the
            information)
        - Update h5debug tool to correctly handle 'huge' & 'tiny' objects.
        - Misc. other code cleanups, etc.

Tested on:
    FreeBSD/32 4.11 (sleipnir)
    Linux/64 2.4 (mir)
    Solaris/64 2.9 (shanti)