hdf5_ep

[svn-r17354] Description:
	Bring r17351 from trunk to 1.8 branch:

	Clean up code (to align w/future sblock_mdc branch changes), tweak
tests for [slightly] easier debugging, fix memory leak when copying chunked
datasets with I/O filters, fix memory leak of free space section when it was
exactly the right size to use for extending an existing block in the file.

Tested on:
       FreeBSD/32 6.3 (duty) in debug mode
	(h5committest performed on trunk)