* Add resolver functions for looking up DNS records of
various types. Currently implemented: MX, TXT, SOA, SRV, NS
* Return records as GVariant tuples.
* Make the GSrvTarget lookups a wrapper over this new
functionality.
* Rework the resolver test so that it has support for
looking up MX, NS, SOA, TXT records, and uses GOptionContext
https://bugzilla.gnome.org/show_bug.cgi?id=672944