Fix #4180: Can't compare Scala and Java Booleans

[smarter]

No description provided.

[Blaisorblade]

Just confirmed those comparisons give the expected result, though I guess this might not warrant a test:

$ /usr/local/bin/dotr
Starting dotty REPL...
scala> val v: java.lang.Boolean = true
val v: Boolean = true
scala> val w: Boolean = true
val w: Boolean = true
scala> v == w
1 |v == w
  |^^^^^^
  |Values of types Boolean and Boolean cannot be compared with == or !=
scala>  implicit def eqSBoolJBool: Eq[Boolean, java.lang.Boolean] = Eq
implicit val eqSBoolJBool: Eq[Boolean, Boolean]
scala> v == w
1 |v == w
  |^^^^^^
  |Values of types Boolean and Boolean cannot be compared with == or !=
scala> w == v
val res0: Boolean = true
scala> w == false
val res1: Boolean = false
scala> implicit def eqJBoolSBool: Eq[java.lang.Boolean, Boolean] = Eq
implicit val eqJBoolSBool: Eq[Boolean, Boolean]
scala> v == w
val res2: Boolean = true
scala> v == false
val res3: Boolean = false