Sort methods lexicographically by signature, and everything < Object

I need a total order on method signatures to be able to select the
'most specific' method. I think this one will give unsurprising
results, so it's good enough for now.

Also: a `'a string' instanceof Object' => `false`, so I need to fudge
things a little. There's some extra corners I'll need to account for
(`null, e.g.).