hdf5_msb

[svn-r17764] Purpose: Fix bug 1483

Description:
H5HG_load made improper assumptions about the ordering of object indices, namely
that they are in order.  Not only is this not guaranteed by the file format
spec, but this condition can be violated if id's "wrap around" which can happen
when overwriting VL data.  H5HG_load has been fixed to handle any order of
indices.  Also fixed some other bugs involving allocation of global heaps in
memory.

Tested: jam, linew, amani (h5committest)