[MLton] basis library -> library project

[Stephen Weeks]

> I'm not sure how big a practical problem this is (in terms of reducing
> upgrade burden), because the basis library seems to be a fairly slowly
> moving target.

True.  My point was that treating the basis differently from other
libraries breaks what was otherwise an ironclad guarantee -- the
meaning of one's code doesn't change unless one chooses to change
library revisions.

> I'm not sure if others like the approach (I'd love to hear critique), but
> I think it would be nice if the public interface code (of each revision)
> of the basis library would be more clearly separated from the
> implementation details.  Like in the extended-basis library:
> 
>   http://mlton.org/cgi-bin/viewsvn.cgi/mltonlib/trunk/com/ssh/extended-basis/unstable/public/

I like that approach.  I think I'll try it in my next library.