hdf5

Merge pull request #2329 in HDFFV/hdf5 from ~DEROBINS/hdf5_der:H5MM_const to develop

* commit '10301154215fb6a22590e80f7b5ed0005f3e1786':
  Minor refactoring to the VFD info free call.
  Updated the 'const memory free' changes based on PR feedback.
  Added a free wrapper that lets us free constant pointers without generating warnings.