conf: single object containing list of IP addresses, list of routes
    
    There are currently two places in the domain where this combination is
    used, and there is about to be another. This patch puts them together
    for brevity and uniformity.
    
    As with the newly-renamed virNetDevIPAddr and virNetDevIPRoute
    objects, the new virNetDevIPInfo object will need to be accessed by a
    utility function that calls low level Netlink functions (so we don't
    want it to be in the conf directory) and will be called from multiple
    hypervisor drivers (so it can't be in any hypervisor directory); the
    most appropriate place is thus once again the util directory.
    
    The parse and format functions are in conf/domain_conf.c because only
    the domain XML (i.e. *not* the network XML) has this exact combination
    of IP addresses plus routes. Note that virDomainNetIPInfoFormat() will
    end up being the only caller to virDomainNetRoutesFormat() and
    virDomainNetIPsFormat(), so it will just subsume those functions in a
    later patch, but we can't do that until they are no longer called.
    
    (It would have been nice to include the interface name within the
    virNetDevIPInfo object (with a slight name change), but that can't
    be done cleanly, because in each case the interface name is provided
    in a different place in the XML relative to the routes and IP
    addresses, so putting it in this object would actually make the code
    more confused rather than simpler).