hdf5_ep

[svn-r22031] Purpose:
  Task for HDFFV-7862 - Select data by chunk direction to improve performance in h5repack

Description:
  h5repack sometimes became very slow when handling big chunked datasets in
  certain cases. (when chunk boundary doesn't match with a hyperslab boundary.)
  The main issue was from figuring out a hypeslab without considering chunk
  boundary to read from and write to such datasets.
  The update was made to figure out a better hyperslab unit with considering
  chunk boundary to improve performance for such cases prior to the update.


Tested:
  jam (linux32-LE), koala (linux64-LE), ostrich (linuxppc64-BE), tejeda (mac32-LE), linew (solaris-BE), Windows