[MLton] extended basis library

[Stephen Weeks]

> because of local, a file which consists of only
> 	val x = x
> is not the same as the empty file. 

You mean, e.g., whether "f.sml" is empty or is the above dec changes
the meaning of an MLB containing the following?

  local
  in 
    f.sml
  end

> It seems a bit awkward to me that local part doesn't go in the file
> itself.

There are certainly some uses where it makes sense to put the local in
the file, and I wish MLton supported it.  But I think that using local
across files makes sense too.  See, e.g. basis.mlb in the extended
basis.