Disallow definitions in refinements

[smarter]

The following should not compile:

object O {
  class A { def f: Int = 0 }
  type X = A { def f: Int = 1 }
}

CC @odersky

[Blaisorblade]

Fixed this year (with tests) in 33e6ca1.

scala> object O {
     |   class A { def f: Int = 0 }
     |   type X = A { def f: Int = 1 }
     | }
3 |  type X = A { def f: Int = 1 }
  |               ^^^^^^^^^^^^^^
  |               illegal refinement