[MLton] MLton and shared libraries

[Stephen Weeks]

> That isn't to discourage, but I think it will take a little hacking of
> MLton to properly generate shared libraries. 
...
> 2) ensuring that the suffix of the top-level program does not exit,
> but instead enters a state where the program is waiting to service
> exported function requests.

I hope this can be easily achieved using Thread_returnToC, as it is
done in SML functions exported via _export.  See the "register"
function in basis-library/mlton/thread.sml.