hdf5

Merge pull request #798 in HDFFV/hdf5 from ~DEROBINS/hdf5_der:misc_windows_warnings to develop

* commit '9fdd984cdea6fce8b5fdd16a7ccc3cc9bbca6fed':
  Changed casts to const void *
  Casted pointers to void to quiet warnings on Linux.
  Added CHECK_PTR_EQ macro to testhdf5 to quiet cast warnings on Windows.
  Fixed misc Warnings flagged by VS2017.