case objects should be handled like case classes and extend Product0

[smarter]

Currently, for a case object like:

case object Foo

we generate an empty object:

final lazy module case val Foo: Foo$ = new Foo$()
final module class Foo$ extends Object { this: <notype> => 
  def <init>(): Unit = {
    super()
    ()
  }
}

But instead, we should generate an object which extends Product0 and overrides the appropriate methods.

[DarkDimius]

fixed in master.