 allocates a handful of objects of a given
size will not build up its own free list for that size.  This avoids
wasting space for unpopular objects sizes or kinds.
<P>
Once the counter passes a threshold, <TT>GC_malloc_many</tt> is called
to allocate roughly <TT>HBLKSIZE</tt> space and put it on the corresponding
local free list.  Further allocations of that size and kind then use
this free list, and no longer need to acquire the allocation lock.
The allocation procedure is otherwise similar to the global f