protocol/packet: accept structs by value for encoding

- server/loginServer: no longer sending packets by pointer, except in cases like AcceptLogin(), which operates on a sent structure slice. since these are already allocated, no need to copy them

protocol/packet.go

@@ -53,7 +53,7 @@ func (pkt Packet) encodeStructField(field reflect.StructField, value reflect.Val
 			return err
 		}
 	default:
-		if err := pkt.Encode(value.Addr().Interface()); err != nil {
+		if err := pkt.Encode(value.Interface()); err != nil {
 			return err
 		}
 	}