hdf5

Merge pull request #2486 in HDFFV/hdf5 from ~DEROBINS/hdf5_der:tools_vol_update to develop

* commit '110cafb9c7b5b9f9170340432062295d630f3ee6':
  Updated tools dump output when dataset offset is undefined.
  Added checks for native optional call support in some of the tools.
  Misc changes for h5dump VOL changes.