Given the socket constructor an options argument

This serves both as a means of giving default values for message-wise
options ('expiry'), but also as a vehicle for socket-wise options
('prefetch', some upcoming which need to be applied during
construction).
Add option 'persistent' (covering durable/deliveryMode=2)
Explain the effect of setsockopt('persistent', false)
Resumable SUB sockets
Why is this line here
Longhand aliases for the socket types

I have grown out of trading characters for obscurity.