Commits
Merge pull request #1393 in HDFFV/hdf5 from ~DEROBINS/hdf5_der:vol_optional_enum_to_macros to develop * commit 'f60e8bb05e3203054e27bf41d0ebc657537736ed': Moved the optional enums to H5VLnative.h and converted to an int typedef and a set of #defines.