Added support spread operator in JS-Backend.

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

@@ -85,7 +85,7 @@ public class FunctionTest extends AbstractExpressionTest {
 
 
     public void testVararg() throws Exception {
-        fooBoxTest();
+        checkFooBoxIsOk();
     }
 
     public void testKT921() throws Exception {

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

@@ -50,7 +50,7 @@ public final class NativeInteropTest extends SingleFileTranslationTest {
     }
 
     public void testVararg() throws Exception {
-        fooBoxTest();
+        checkFooBoxIsOk();
     }
 
     public void testUndefined() throws Exception {