hdf5_der

[svn-r24064] Purpose:
	Updates the use_append_mmchunks test to use the most recent file
	format.  This switches the chunk index type from version 1 B-tree
	(which is not SWMR-safe due to the lack of a checksum) to 
	extensible array.

	This fixes the SWMR-6 issue in JIRA.

	Also cleaned up the code a little so it compiles without warnings.

Tested on:
	jam (32-bit linux)