Neighbor cache is unware of addresses added or removed without taking the interface down

Hi, when playing with bird I noticed the following problem: When I add or remove addresses to/from an interface without taking the interface down when doing so, the neighbor cache isn't notified, causing BGP sessions not to start even though the neighbor has become reachable, or BGP sessions that already found their neighbor not to look for it on other interfaces after the address has disappeared. The attached patch fixes this by updating the neighbor cache on every interface address update; I've only tested it with BGP though, I don't know if it has any side effects concerning other protocols. Best regards, Matthias Schiffer