[MLton] Problems with Primitive.MLton visibility

[Stephen Weeks]

> I'm trying to deal with path issues in basis-library/system/path.sml.
> To do so, I was trying to access the Primitive.MLton.Platform.OS value,
> but for some reason, MLton fails during the compile complaining that
> MLton is an unknown value.
> 
> val isWin32 = let open Primitive.MLton.Platform.OS in
>                         case host of
>                             Mingwin => true
>                         |   _ => false

Did you mean Primitive.MLton.Platform.OS.host ?