Add tests on callable references

Object members and accessors for private class members

compiler/testData/codegen/box/callableReference/objectMemberUnitOneStringArg.kt

@@ -0,0 +1,13 @@
+object A {
+    var result = "Fail"
+    
+    fun foo(newResult: String) {
+        result = newResult
+    }
+}
+
+fun box(): String {
+    val x = A::foo
+    A.x("OK")
+    return A.result
+}