Add labels for extension properties

#KT-2824 Fixed

compiler/testData/codegen/label/propertyInClassAccessor.kt

@@ -0,0 +1,17 @@
+class Test {
+    val Int.innerGetter: Int
+        get() {
+            return this@innerGetter
+        }
+
+    fun test(): Int {
+        val i = 1
+        if (i.innerGetter != 1) return 0
+        return 1
+    }
+}
+
+fun box(): String {
+    if (Test().test() != 1) return "inner getter or setter failed"
+    return "OK"
+}