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

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

@@ -0,0 +1,27 @@
+package
+
+package p {
+    internal fun foo(): p.Foo.Nested?
+
+    internal final class Bar : p.Foo {
+        public constructor Bar()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        internal final fun foo(): p.Foo.Nested?
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    internal open class Foo {
+        public constructor Foo()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+        protected final class Nested {
+            public constructor Nested()
+            public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+            public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+            public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+        }
+    }
+}