Added tests

backend.native/tests/codegen/propertyCallableReference/varExtension.kt

@@ -0,0 +1,21 @@
+class A(y: Int) {
+    var x = y
+}
+
+var A.z: Int
+    get() = this.x
+    set(value: Int) {
+        this.x = value
+    }
+
+fun main(args: Array<String>) {
+    val p1 = A::z
+    val a = A(42)
+    p1.set(a, 117)
+    println(a.x)
+    println(p1.get(a))
+    val p2 = a::z
+    p2.set(42)
+    println(a.x)
+    println(p2.get())
+}