hdf5

Merge pull request #1311 in HDFFV/hdf5 from ~DEROBINS/hdf5_der:cmake_tweaks to develop

* commit 'c9273522e9a7e946802d8545b2532f9129b459a9':
  Updated RELEASE.txt to reflect HDFFV-10609 work (H5Xpkg.h files being incorrectly installed).