Proposal: MaxTenuringThreshold and age field size changes

[Y Srinivas Ramakrishna]

> 
> The lesson here is promotions are much more expensive than copies. I
> thought I'd share that.

And, just to state the somewhat obvious warning, for the benefit of the unwary ...
the relative costs of the two depend on what the old generation
allocator/collector are vs the young generation collector. So you might
need to retune were you to use a different memory manager for the old generation,
for example.

-- ramki