hdf5_ep

[svn-r18499] Description:
	Bring r18498 from trunk to 1.8 branch:

	Bring r18497 from metadata journaling "merging" branch to trunk:

	Extract data structure 'destroy' routines from metadata cache client
'destroy' callbacks.

Tested on:
	FreeBSD/32 6.3 (duty) w/debug
	(h5committested on trunk)