Some enum-related fixes

(NB: testEnumClass3 doesn't work yet, effective modality required for enum class)

compiler/testData/ir/box/enumClass.kt

@@ -1,3 +1,16 @@
-enum class Test { OK }
+fun <T> assertEquals(actual: T, expected: T) {
+    if (actual != expected) {
+        throw java.lang.AssertionError("Assertion failed: $actual != $expected")
+    }
+}
 
-fun box() = Test.OK.toString()
+enum class Test {
+    OK
+}
+
+fun box(): String {
+    assertEquals(Test.OK.ordinal, 0)
+    assertEquals(Test.OK.name, "OK")
+    
+    return "OK"
+}