config.h namespace clashes

[Simon Marlow]

> The inclusion of the GHC made config.h in HsFFI.h makes it extremely
> difficult to use autoconf with ones own projects without dealing with
> horrible name clashes everywhere. Is there some way this can be fixed?
> perhaps pre-generating the HsFFI.h.
> 
> although I don't think it is stated explicitly by the FFI 
> report, I would
> assume that HsFFI.h should not clash with anything that doesn't start
> with Hs, hs_ or HS_.
> 
> also, it would be good if config.h could be renamed to something like
> ghc-config.h, because otherwise the conflict between the 
> names can hide
> bugs where you get the incorrect config.h or make it tricky to get at
> the GHC one if it is actually the one you want.

Yes, we should definitely do that.  I'm surprised this hasn't caused
problems before (or maybe it has?).

Cheers,
	Simon