Extending Library interface

If an interfaces that extend the Library interface is created using deferred binding, there is one strict limitation: the extended interface can not contain any methods.

Library instances are generated using LibraryGenerator, which does not known how to implement any methods specified in the extended interface. If this limitations presents a big problem later on, it can be relaxed by adding a new annotation which specifies the name to a delegate class implementing these methods, which the generator can forward each unknown method to. It will however be difficult to make this solution work reliably, because of all the different edge-cases which must be handled.