Enum classes lowering.

compiler/testData/ir/irText/classes/enumWithSecondaryCtor.kt

@@ -0,0 +1,21 @@
+// WITH_RUNTIME
+
+enum class Test1(val x: Int) {
+    ZERO, ONE(1);
+    constructor() : this(0)
+}
+
+enum class Test2(val x: Int) {
+    ZERO {
+        override fun foo() {
+            println("ZERO")
+        }
+    },
+    ONE(1) {
+        override fun foo() {
+            println("ONE")
+        }
+    };
+    constructor() : this(0)
+    abstract fun foo()
+}