KT-1519: Error calling native extension function from user defined extension function.

js/js.translator/testFiles/native/cases/KT-1519.kt

@@ -0,0 +1,19 @@
+package foo
+
+native
+class Wow() {
+    val x : Int = js.noImpl
+    val y : Int = js.noImpl
+}
+
+native
+fun Wow.sum() : Int = js.noImpl
+
+fun Wow.dblSum() : Int {
+    return 2 * sum()
+}
+
+
+fun box() : Boolean {
+    return (Wow().dblSum() == 6)
+}