[cpp-threads] memory model

[Doug Lea]

> 
> 
> I'll take a look, but can you give me some hints about what I need to look 
> for?

Examples that are race-free but without classically-defined control
dependencies.

But to get back to the main point, the basic question here is,
Do these special msync forms describe properties that are already in the
code itself? If so, someday those forms will seem just
as quaint as "register" qualifiers.

Or, in other words, are there cases where a sufficiently good optimizer
that did not use the special forms would NOT be able to weaken a barrier
because of upcoming dependent loads, etc?

-Doug