#KT-3257 Fixed - Bad diagnostics when trying to instantiate a private class

Hi,

I've committed some changes to fix "KT-3257". the messages will is like following now:

```kotlin
class A {
    private class B
    public class C private()

    private fun bar() {}
}

fun foo() {
    A.B()     // ERROR 1: Cannot access 'B': it is 'private' in 'A'
    A.C()     // ERROR 2: Cannot access '' : it is 'private' in 'C'

    A().bar() // ERROR 3: Cannot access 'bar' : it is 'private' in 'A'
}
```