hdf5_ep

[svn-r16306] Description:
	Bring r16305 back from revise_chunks branch:

	Add detection of C99 "designated initializers" to configure script and
use new H5_HAVE_C99_DESIGNATED_INITIALIZER macro to conditionally compile
default layout variables in src/H5Pdcpl.c

	Also, minor code cleanups, etc.

Tested on:
	FreeBSD/32 6.3 (duty) in debug mode
	(Other platforms tested on branch)