Make read-write info cascade through entries, not nodes (potentially less optimized, but safer and correctly handles branching)

Change lock checking method semantic: they now check if themselves are locked, not if their parent object are locked

Messy commit: handle autolocked cyobj + delegate lock checking to subexpr mechanism + some more checks (bool nodes)

Make declaration of cypclass methods work when declaring without defining a pointer type as return type

Hacky way to make const cypclass behave as const in Cython but not in C++ (useful for refcount bookkeeping for example)

Fix C++ garbage when trying to access __constructor__: generate each constructor wrapper as a static method inside the class