Allow native objects in package objects without @JSName

[japgolly]

These two snippets are equivalent:

1:

package foo.bar

import scalajs.js

@js.native
object Ah extends js.Object

2:

package foo

import scalajs.js

package object bar {
  @js.native
  object Ah extends js.Object
}

Yet the second snippet fails compilation with

[error] ah.scala:7: Native JS objects inside non-native objects must have an @JSName annotation
[error]   object Ah extends js.Object

[sjrd]

Indeed, that makes sense.