hdf5_ep

[svn-r3881] Purpose:
    Feature
Description:
    The allocation by alignment (H5Pset_alignment) feature code somehow
    got dropped in some 1.3.x version.
Solution:
    Re-implemented it with "new and improved" algorithm.  It keeps track
    of "wasted" file-fragment in the free-list too.
Platforms tested:
    modi4(parallel).