hdf5_der

Merge pull request #187 in HDFFV/hdf5 from ~VCHOI/my_hdf5_fork:page_buffering to page_buffering

* commit '7ebca389b6f361ac5541228c3b9d0171296c834d':
  Modifications to fix bugs when extending and shrinking large-sized sections (1) When extending a large-sized block at EOA, put the mis-aligned fragment into the free-space manager. (2) When shrinking large-sized sections, free only full pages and retain partial page in the free-space manager. The above is done to keep EOA at page boundary.