hdf5_ep

Merge pull request #495 in HDFFV/hdf5 from ~BMRIBLER/hdf5_1_8_bmr:hdf5_1_8 to hdf5_1_8

* commit '6c161ba4dc7c25da6ecbe98aec10fff7b1365df6':
  Fixed a comment.
  Code improvement Description:     - Moved class H5File to inherit from class Group because an HDF5 file is       a root group     - Cleanup header file inclusion and class forward declaration     - Revised comments Platforms tested:     Linux/32 2.6 (jam)     Linux/64 (platypus)     Darwin (osx1010test)