Reliable sender's connection replies has a potential ordering issue

[samlaf]

Hello.

I think there is a bug in reliable sender's connection's pending replies queue ordering, but please let me know if it is my understanding that is lacking.

If we send multiple messages to a peer, there is no reason that the acknowledgements will be received in the same order. Yet the code seems to assume that because it is sending the received ACK message to the first handler in the queue (pop_front).