hdf5

Merge pull request #1388 in HDFFV/hdf5 from ~DEROBINS/hdf5_der:vol_optional_enum_to_macros to develop

* commit '9f175afce8c08bf6193e45ce391e05e4198dd61c':
  Updated va_arg-->HDva_arg in the native VOL connector.
  Added HD to va_* calls in a couple of library files.