Add separate compilation test case for #3339

Author: odersky

tests/run/i3339/A_1.scala

@@ -0,0 +1,5 @@
+package outer {
+  private class A() {
+    override def toString = "A"
+  }
+}

tests/run/i3339/B_2.scala

@@ -0,0 +1,9 @@
+package outer {
+  package inner {
+    object Test {
+      def main(args: Array[String]): Unit = {
+        println(new A())  // now ok
+      }
+    }
+  }
+}

tests/run/i3339/Test_3.scala

@@ -0,0 +1,3 @@
+object Test extends App {
+  outer.inner.Test.main(Array())
+}