netconf: add support for neighbor proxy attribute

Report changes to proxy_arp/proxy_ndp attribute.
diff --git a/ip/ipnetconf.c b/ip/ipnetconf.c
index 9a77ecb..7353f59 100644
--- a/ip/ipnetconf.c
+++ b/ip/ipnetconf.c
@@ -114,6 +114,10 @@
 		fprintf(fp, "mc_forwarding %d ",
 			*(int *)RTA_DATA(tb[NETCONFA_MC_FORWARDING]));
 
+	if (tb[NETCONFA_PROXY_NEIGH])
+		fprintf(fp, "proxy_neigh %s ",
+			*(int *)RTA_DATA(tb[NETCONFA_PROXY_NEIGH])?"on":"off");
+
 	fprintf(fp, "\n");
 	fflush(fp);
 	return 0;