private method callable from other module

[kdevel via Digitalmars-d-learn]

Is this a known bug?

```
// file b.d
import std.stdio;

struct S {
   private void foo (ubyte c)
   {
      writeln (__PRETTY_FUNCTION__);
   }
   void foo ()
   {
   }
}
```

```a.d
// file a.d
unittest {
   import b;
   auto s = S ();
   s.foo ('x');
}
```

```
$ dmd -g -unittest -main a.d b.d
$ ./a
void b.S.foo(ubyte c)
1 modules passed unittests
```