JS backend: generate ref for not public api open classes as ref to internal class pool (_c var), but not to namespace definition.

(cherry picked from commit fa3db43)

js/js.translator/testFiles/trait/cases/checkImplementationCharacteristics.kt

@@ -1,9 +1,9 @@
 package foo
 
-trait A {
+public trait A {
   fun foo() {}
 }
-trait B : A {
+public trait B : A {
   fun boo() {}
 }
 
@@ -12,7 +12,6 @@ native val undefined: Any = noImpl
 native class Function(vararg args: String)
 
 val hasProp = Function("obj, prop", "return obj[prop] !== undefined") as ((Any, String)->Boolean)
-val PREFIX = "Kotlin.modules.JS_TESTS.foo"
 
 fun box(): String {
   val a = object: A {}
@@ -24,6 +23,9 @@ fun box(): String {
   if (!hasProp(b, "foo")) return "B hasn't foo"
   if (!hasProp(b, "boo")) return "B hasn't boo"
 
+  val PREFIX = "Kotlin.modules.JS_TESTS.foo"
+  if (eval("$PREFIX.A") == null) return "$PREFIX.A not found"
+  if (eval("$PREFIX.B") == null) return "$PREFIX.B not found"
   if (eval("$PREFIX.A === $PREFIX.B") as Boolean) return "A and B refer to the same object"
 
   return "OK"