[MLton] Dependencies, -stop f and mlb-files

[Matthew Fluet]

> The -stop f option generates a list of files, which is useful for dependencies
> in a Makefile, but omits the mlb-files.  Is there some reason for this?

I have a vague recollection that we decided to omit the mlb-files, but I 
can't recall if that is actually true or what the reason was.  I'll 
search the archive a little.

> I'd prefer that it included the mlb-files, because is easy to filter them out
> (e.g. grep -v '\.mlb$'), but omiting them results in incomplete dependencies.

I tend to agree.  Your patch looks good, so long as it doesn't have any 
adverse affects on the build process.