Fixed KT-4085 Usability problem: Can't import protected nested class

#KT-4085 Fixed

compiler/testData/diagnostics/tests/imports/ImportProtectedClass.kt

@@ -0,0 +1,13 @@
+package p
+
+import p.Foo.Nested
+
+open class Foo {
+    protected class Nested
+}
+
+class Bar: Foo() {
+    fun foo(): Nested? = null
+}
+
+fun foo(): <!INVISIBLE_REFERENCE!>Nested<!>? = null