ForeignDependencies: The Semantics

[Alastair Reid]

John, thanks for the case analysis - that made it much clearer what
ForeignDependencies are (and are not).

All sounds good.  

> For Hugs & NHC, it would probably suffice to keep a list of
> dependencies in the ForeignPtr.  After GC, you have to repeatedly
> traverse the live ForeignPtrs making each of the dependencies live,
> until you can make no more ForeignPtrs live, then finalize the dead
> ones.

Yup, there's lots of code like that in Hugs already so it should be
easy enough to add.

--
Alastair