Make it possible to add an IPv6 host route to a host directly connected.

Use something like this:
route add -inet6 <dest_addr> <my_addr_on_that_interface> -interface -llinfo

This is usefull for wireless adhoc mesh networks.

MFC after:	5 days

sys/netinet6/nd6.c

@@ -1390,6 +1390,8 @@ nd6_rtrequest(req, rt, info)
 					    ip6_sprintf(&llsol), error));
 				}
 			}
+		} else if (req == RTM_ADD && SDL(gate)->sdl_alen == 0) {
+			ln->ln_state = ND6_LLINFO_INCOMPLETE;
 		}
 		break;