hdf5_ep

Merging in latest from upstream (HDFFV/hdf5:refs/heads/hdf5_1_8)

* commit '394c6b8c3a4c781c1ee877f969a146cece3d7831':
  Add missing EXPORT tag in install command
  Fix typo and remove test only tools from exports
  Add namespace and export utils
  HDFFV-9961: Merge GIT ext lib option to 1.8