JS backend : added test for local extension function.

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

@@ -131,4 +131,8 @@ public class FunctionTest extends AbstractExpressionTest {
     public void testManglingAnyMethods() throws Exception {
         checkFooBoxIsOk();
     }
+
+    public void testLocalExtFunction() throws Exception {
+        checkFooBoxIsOk();
+    }
 }

js/js.translator/testData/expression/function/cases/localExtFunction.kt

@@ -0,0 +1,9 @@
+package foo
+
+fun box(): String {
+    fun String.test(i: Int) = this + i + "OK"
+    val a = "foo".test(32)
+    if (a != "foo32OK") return "$a"
+
+    return "OK"
+}