hdf5_chunking_query_bmr

[svn-r17399] Description:
	Bring r17393 and r17398 from trunk to 1.8 branch:

Bring back more changes from the file free space branch to the trunk. (17393)

First set of changes to move VFD 'truncate' call out of H5F_flush and defer
it until the file is closed. (17398)

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