Fix #1287: Add regression test

Author: nicolasstucki

tests/pos/i1287/Foo.scala

@@ -0,0 +1,3 @@
+private object Foo {
+  val x: Int = 1
+}

tests/pos/i1287/Test.scala

@@ -0,0 +1,3 @@
+object Test {
+  val a = Foo.x
+}