vchoi_fork

[svn-r19076] Purpose: Fix bug 1951

Description:
A bug introduced in 1.8.5 causes local heap data blocks to be mis-aligned when
sizeof_offsets + 2*sizeof_lengths is not a multiple of 8.  In this case, the
address of the data block as stored in the heap prefix is aligned but the actual
data block is not.  This causes files created with these sizes to be corrupted,
and prevents uncorrupted files with these sizes to be unreadable.  Modified
local heap code to account for alignment.

Tested: jam, amani, linew (h5committest)