hdf5_ep

[svn-r17941] Description:
	Bring r17939 from trunk to 1.8 branch:

	Handle external links from symlinked files by adding another check to
look for "child" files for links from the actual location of the "parent" file,
instead of from the location of the symlink.

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