ArrayList improvements:

1) remove must compare object using Kotlin.equals (the same as in contains)
2) use ArrayIterator instead of ListIterator (perfomance)
3) remove duplicated code (refactor)
4) toArray
5) fix "add((index, item)" — correct translation to JavaScript "addAt"

js/js.tests/test/org/jetbrains/k2js/test/semantics/ArrayListTest.java

@@ -51,6 +51,10 @@ public final class ArrayListTest extends JavaClassesTest {
         fooBoxTest();
     }
 
+    public void testToArray() throws Exception {
+        fooBoxTest();
+    }
+
     public void testIndexOOB() throws Exception {
         try {
             fooBoxTest();