Work for bugzilla 1754: h5diff: support comparing through links. Description: merged from hdf5 trunk (18164, 18165, 18166, 18167, 18170, 18266, 18273) Tested: h5committest (jam, amani and linew)
Add test case relate to bug1749. Also corrected command echo line which is not match with actual test. Tested on Jam.