util: make inherits work with classes

The current implementation overwrites the prototype of the target
constructor. It is not allowed with ES2015 classes because the prototype
property is read only. Use Object.setPrototypeOf instead.

Fixes: https://github.com/nodejs/node/issues/3452
PR-URL: https://github.com/nodejs/node/pull/3455


Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>