hdf5_ep

[svn-r21566] Description:
    Bring r21561 from trunk back to 1.8 branch:

    Correct error in loading local heap prefix & data block from the file.
Sometimes the local heap's prefix could be loaded before the data block (e.g.
using H5Oget_info), but then when the data block was loaded later, the free
list information would get lost, causing the heap's size to grow larger than
necessary.  This is Jira bug #HDFFV-7767

Tested on:
    Mac OS X/32 10.7.2 (amazon) w/debug
    (h5committest coming up)