_G_USING_THUNKS + Sparc

[Benjamin Kosnik]

> Why do we set this to zero on Solaris systems?

I have no idea.

> I don't understand how all of this is supposed to work.
> Don't we control how the whole thing is layed out because
> we build our own libio?  Or is there some other dependency
> with how the system C library implements things?

No libio is built.

> I'm investigating some libstdc++ sparc-linux failures
> and noticed this anomaly.

Thanks for looking at these. I've noticed that sparc-solaris2.8 results
also seem dodgy.

-benjamin