netlink: fix IPv6 RA flag retrieval

The RA flags aren't in the link flags, they are in the special
PROTINFO flags that the IPv6 stack sends.  To get these, because
libnl doesn't have native support for them, we get to parse the
netlink messages directly.  Furthermore, the PROTINFO message
isn't sent unless it's explicitly requested with a
RTM_GETLINK/AF_INET6 message, meaning we get to poll for it
periodically.

So switch over to the netlink monitor object (killing a lot of
duplicate code) and start requesting the PROTINFO bits from
netlink.

src/nm-netlink-monitor.c

@@ -442,6 +442,28 @@ nm_netlink_monitor_unsubscribe (NMNetlinkMonitor *self, int group)
 	set_subs (self, group, subs);
 }
 
+/***************************************************************/
+
+gboolean
+nm_netlink_monitor_request_ip6_info (NMNetlinkMonitor *self, GError **error)
+{
+	NMNetlinkMonitorPrivate *priv;
+
+	g_return_val_if_fail (self != NULL, FALSE);
+	g_return_val_if_fail (NM_IS_NETLINK_MONITOR (self), FALSE);
+
+	priv = NM_NETLINK_MONITOR_GET_PRIVATE (self);
+
+	/* FIXME: nl_rtgen_request() gets the return value screwed up with
+	 * libnl-1.1; revisit this and return a proper error when we port to
+	 * a later libnl.
+	 */
+	nl_rtgen_request (priv->nlh, RTM_GETLINK, AF_INET6, NLM_F_DUMP);
+
+	return TRUE;
+}
+
+
 static gboolean
 deferred_emit_carrier_state (gpointer user_data)
 {