Drop fakemodule

[ not for 1.0 ] 

After PR #3555, I don't think we have any need for our FakeModule class, so this removes it in favour of just using ModuleType.

There shouldn't be any user-visible benefit, so we could leave this until after release if we're going into stability mode. On the other hand, it changes an (undocumented) API, so we might prefer to do this before 1.0.