hdf5_msb

[svn-r13287] Description:
	Add H5Aget_info_by_idx & H5Aget_name_by_idx routines, along with
refactoring underlying indices code to handle those sort of queries.

	Simplify the link callback routines a bit.

	Minor other cleanups.

Tested on:
	Mac OS X/32 10.4.8 (amazon)
	FreeBSD/32 6.2 (duty)