Fixing up `Prims.replaceItem`
Fixing up `Prims.sublist`

My version and the old version compile to the same code, but I really
hate `..` and `...` CoffeeScript, because I can never remember which one
means what.  `slice` is pretty clear to me.
Fixing up `Prims.sentence`
Fixing up `Prims.breedOn`
Fixing up `Prims.variance`