Module internal types are not implicitly available anymore simply by placing
them inside the module's main directory. It is now necessary to mention them
as internal types in the qmldir file.
See qtdeclarative commits 22a2cc43387ec3b9f74a6c01f8665378a4541147 (introduced
the change) and 930aea8b9ca59a24838cf7f279653e3b2ee40cee (explanation)