Poll: System.exitWith behaviour

[Simon Marlow]

> I think, having the third point is good, because the Haskell
> report requires that=20
>=20
>   Computation exitWith code terminates the program,
>   returning code to the program's caller.

Either way we still conform to the report in the case of a single
threaded program (actually, we've already deviated from the report in
allowing you to catch the ExitException and carry on).

For a multi-threaded program, it's not clear to me what exitWith should
do.  What should happen if a Haskell callback invokes exitWith?  Should
it terminate the Haskell main thread?

I must admit I'm leaning more towards omitting the third point, and
that's what I've implemented for now.

Cheers,=09
	Simon