COMP: Fix HDF5 add_custom_command TARGET does not exist warnings.

Comment out the invalid syntax of the commands.  They are not used --
versions of H5Edefin.h, H5version.h, and H5overflow.h were committed to the
source tree.

This fixes warnings related to CMake Policy CMP0040, the TARGET of an
add_custom_command argument must exist.

Change-Id: I959a78736320729e8047116335676046e3e6af74
Merge topic 'hdf5-custom-command'

797d9f1 COMP: Fix HDF5 add_custom_command TARGET does not exist warnings.