Check for exposed local classes (or objects) in type signatures

compiler/testData/codegen/box/objects/objectLiteralInClosure.kt

@@ -1,6 +1,6 @@
 package p
 
-class C(val y: Int) {
+private class C(val y: Int) {
     val initChild = { ->
         object {
             override fun toString(): String {

compiler/testData/codegen/boxWithStdlib/regressions/kt3850.kt

@@ -1,6 +1,7 @@
-class One {
+private class One {
     val a1 = arrayOf(
             object { val fy = "text"}
-    )}
+    )
+}
 
 fun box() = if (One().a1[0].fy == "text") "OK" else "fail"