Make enum classes comparable

#KT-3727 Fixed

core/builtins/native/kotlin/Enum.kt

@@ -16,10 +16,12 @@
 
 package kotlin
 
-public abstract class Enum<E : Enum<E>>(name: String, ordinal: Int) {
+public abstract class Enum<E : Enum<E>>(name: String, ordinal: Int): Comparable<E> {
     public final fun name(): String
     public final fun ordinal(): Int
 
+    public override final fun compareTo(other: E): Int
+
     public override final fun equals(other: Any?): Boolean
     public override final fun hashCode(): Int
     public override fun toString(): String