Improve JIT debugging when setup fails
Add specs for Array#values_at with weird Range

* https://github.com/rubinius/rubinius/pull/2490#pullrequestreviewcomment-5347303
* https://github.com/rubinius/rubinius/pull/2490#pullrequestreviewcomment-5347339
Fix Array#values_at with weird Range for 2.0