JS: make enum valueOf() throw if not found.

js/js.translator/testData/kotlin_lib.js

@@ -207,6 +207,10 @@ Kotlin.throwCCE = function () {
     throw new Kotlin.kotlin.ClassCastException("Illegal cast");
 };
 
+Kotlin.throwISE = function (message) {
+    throw new Kotlin.kotlin.IllegalStateException(message);
+};
+
 /** @const */
 var POW_2_32 = 4294967296;
 // TODO: consider switching to Symbol type once we are on ES6.