hdf5_ep

[svn-r15016] Description:
    Port revision 15015 back to 1.8 branch:

>     Detect chunks that are >4GB before dataset gets created and return error
> to application.
> 
>     Tweak lots of internal variables that hold the chunk size/dimensions to
> use an 'uint32_t', instead of a 'size_t', so that the integer size is constant.
> 
>     Correct a number of our tests which were creating datasets with chunks
> that were >4GB and add some specific tests for >4GB chunk size detection.
> 
>     Minor whitespace & other code cleanups.

Tested on:
    Mac OS X/32 10.5.2 (amazon)
    Forthcoming testing on other platforms...