[MLton] upcoming public release

[Matthew Fluet]

> The only other thing on my list of musts for the release is to split
> out the mlb spec from the user guide into a separate document.  Then,
> we can live with it as pdf only, although it would be nice to make it
> available as html someday.  Matthew, can you do this?

Yes, that's easy to take care of.

> * Caching preprocessing of the basis.  Matthew, where are you on this?

I gave it a little more thought, and it is probably more difficult than I
originally thought. But I'll try to write up what I think might work and
where the problems lie.