Make enum classes comparable

#KT-3727 Fixed

js/js.translator/testData/enum/cases/enumIsComparable.kt

@@ -0,0 +1,24 @@
+package foo
+
+enum class A {
+    one
+    two
+}
+
+fun box(): String {
+    val x = A.one.compareTo(A.two)
+    if (x != -1) return "Fail cmp(one, two) = $x"
+    val y = A.two.compareTo(A.one)
+    if (y != 1) return "Fail cmp(two, one) = $y"
+
+    if (!(A.one < A.two)) return "Fail !(one < two)"
+    if (A.one >= A.two) return "Fail one >= two"
+
+    if (!(A.two > A.one)) return "Fail !(two > one)"
+    if (A.two <= A.one) return "Fail two <= one"
+
+    val z = A.one.compareTo(A.one)
+    if (z != 0) return "Fail cmp(one, one) = $z"
+
+    return "OK"
+}