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)
Bug fix
PG compiler complains about array out of bounds (a rank of zero was not checked)
Adding a scalar dataset to the test generator program. this case is run on a previous existing run, the case was added to 2 existing files
Tested: windows, linux
