hdf5

Merge pull request #786 in HDFFV/hdf5 from ~LRKNOX/hdf5_lrk:hdf5_1_8_20 to hdf5_1_8_20

* commit 'ec34b34767482ceccd87159c401a7db13c7dc505':
  Switch default build mode from development to production. Increment version string to pre2.