vchoi_fork

[svn-r19473] Description:
	Bring r19472 from trunk to the 1.8 branch:

	Create a new, more streamlined method of generating I/O sequences when
there is only a single block defined by a hyperslab.  This improves the
performance of Ger Van Diepen's (LOFAR team) benchmark by about 20%.

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