Patch to fix BGP ghost routes resulting from loops

I've created attached patches to prevent BGP route loops from turning into ghosts (issue reported earlier to the mailing list: http://marc.info/?l=bird-users&m=129433651229774&w=2). Instead of completely ignoring received BGP routes containing the router's own AS number, it should now handle them as if the prefixes are unreachable. We have tested the patch against git and it fixed the issue there. I've also made an (untested) patch against bird 1.2.5. -- Ivo