hdf5_ep

Merge pull request #1605 in HDFFV/hdf5 from merge_hyperslab_update_01 to develop

* commit '08b009cc4ab2a8d8d289697d6d4688c0e5c53c6e':
  Clean up if-else chain.
  Remove thread-local copy of hyperslab operation generation value.
  Core changes to selection code from the hyperslab_updates branch.