Search directive from resolv.conf had a maximum of 8 domains. Any
more were ignored. Do not ignore them anymore; iterate over any
number of domains.
Test resolv.conf support by checking the first and last domain in
the search list. Ignore the domains between; just ensure that the
last domain in the configuration is the last domain parsed.
Only call eatline() to skip to the next line if we're not
already at the end of a line when parsing an unknown directive.
We were accidentally skipping the next line when there was only
a single unknown directive on the current line.
Coverity detected that address->type.sa was too small when copying
a struct sockaddr_sin6, use the alterative union element
address->type.sin6 instead.
After removing sockaddr_unix from isc_sockaddr, we can also remove
sockaddr_storage and reduce the isc_sockaddr size from 152 bytes to just
48 bytes needed to hold IPv6 addresses.
`libirs` used to be a reference implementation of `getaddrinfo` and
related modern resolver APIs. It was stripped down in BIND 9.18
leaving only the `irs_resconf` module, which parses
`/etc/resolv.conf`. I have kept its include path and namespace prefix,
so it remains a little fragment of libirs now embedded in libdns.
