Refcounting bug on nested scope

[AndrewAday]

class Foo {}

{
    Foo foo;
    // do stuff
}

// after exiting scope, foo refcount is not properly decremented, destructor is not called

[gewang]

fix committed in c56efceeee41b06ef8d2b2ae453daafef797243a unit test in 90f966cb8649840bc05f5d77219867593eb7fe94