[krbdev.mit.edu #1380] Duplicate DNS Lookups make krb5_init_creds slow

[Ken Raeburn via RT]

Additional information from lxs: Apparently lookupd does cache the
results of gethostbyname; it just doesn't cache the results of
getaddrinfo.  So this is largely Apple's bug.

Open question: What about res_search?  That's how we do the SRV
queries.