Reworked and enhanced extreme sanity check in H5C.c, fixing an 
uninitialized variable bug in passing.

Added the H5C_get_entry_ptr_from_addr() and H5C_verify_entry_type()
in H5C.c, along with their pass through functions in H5AC.c.  Note
that H5C_get_entry_ptr_from_addr() is quite slimey, and should be
avoided if possible.

Updated fractal heap to use flush ordering to force children
in the hdr / iblock / dblock tree to be flushed prior to parents.
This is part of a port of the fractal heap to the V3 cache, although
I gather that it will also be useful for SWMR.

Added sanity checking code to the fractal heap to verify that direct 
blocks are flushed before their parent indirect blocks, child indirect
block are flushed prior to their parent indirect blocks, and that the
root iblock or dblock is flushed prior to the header

Tested on:

        Jam: Serial and parallel
        Phoenix (Debian): serial, debug and production
        amazon (MacOS): serial



git-svn-id: https://svn.hdfgroup.uiuc.edu/hdf5/trunk@25321 dab4d1a6-ed17-0410-a064-d1ae371a2980