vchoi_fork

[svn-r4842] Purpose:
    Feature improvement
Description:
    Re-write how the free-list headers were used, to reduce the amount of space
    added to each malloc request.  Reduced header for array and block free
    list items from 24 bytes to 8 bytes and eliminated the header for fixed-size
    free list items entirely.  This should reduce the amount of memory that the
    library uses.
Platforms tested:
    FreeBSD 4.5 (sleipnir) & IRIX64 6.5 (modi4)