'When' buffer: messages should only be unpickled at time of delivery

[juanjgalvez]

Messages stored in _when_buffer should probably not be unpickled before buffering. Instead they should be unpickled after retrieving them from buffer. The reason is that if an object with buffered messages migrates, these messages will have to be pickled and unpickled for each time the object migrates.

[juanjgalvez]

Note that this is not a common occurrence (usage of when buffers plus having undelivered messages in these buffers plus having these objects migrate). So this is considered low priority.