vchoi_fork

Remove #if 0'd quick fix for the free-space management bug in
src/H5MF.c.

Also, squashed commit of the following:

commit adcf8a315e82c0848d126e7e46b662930c081896
Author: Vailin Choi <vchoi@jam.ad.hdfgroup.org>
Date:   Mon Dec 2 11:07:25 2019 -0600

    Fix the FSM bug when setting the FSM threshold to a non-default value.
    Check for smaller or larger section size after merging and shrinking a section,
    for this case is the section that is smaller than threshold (see H5MF_xfree() in H5MF.c).
    It is possible for the section to be smaller after merging/shrinking (see H5MF__sect_large_shrink()
    in H5MFsection.c).