KT-1417 & KT-1398 proper access flags for backing fields

compiler/testData/codegen/regressions/kt1398.kt

@@ -0,0 +1,7 @@
+open class Base(val bar: String)
+
+class Foo(bar: String) : Base(bar) {
+  fun something() = (bar as java.lang.String).toUpperCase()
+}
+
+fun box() = Foo("ok").something()

compiler/testData/codegen/regressions/kt1417.kt

@@ -0,0 +1,9 @@
+package pack
+
+open class A(val value: String )
+
+class B(value: String) : A(value) {
+    fun toString() = "B($value)";
+}
+
+fun box() = if (B("4").toString() == "B(4)") "OK" else "fail"