Fix property list constants with HDF5 1.8.14

This resolves the issue of using the HDF5 module with library version 1.8.14, as reported in
https://groups.google.com/forum/#!topic/julia-users/rlNs3m8xXJ0

For details on the ABI breakage, see http://www.hdfgroup.org/HDF5/doc/ADGuide/Compatibility_Report/CR_1.8.14.html