vchoi_fork

[svn-r12770] Description:
    Overhaul usage of object header chunks to reduce I/O operations and
memory allocations.  The object header prefix is now stored in the first
object header chunk's "image" in memory.

    Also, lots of formatting cleanups.

    Taught h5debug tool about new object header format (which isn't enabled
just yet).

Tested on:
    Linux/32 2.6 (chicago)
    Linux/64 2.6 (chicago2)