Missing glue when returning referrals

IBDNS does not return any glue records with referrals. This breaks recursive resolvers when trying to resolve a domain name with in-bailiwick name servers.

If those referrals refer to in-bailiwick name servers, resolutions will fail no matter what. This issue is further discussed in draft-ietf-dnsop-glue-is-not-optional, which also provides some useful examples.

Omitting the glue is an interesting failure mode that could be enabled by configuration.