For server-side sockets, no longer pass the server object to the
js constructor. This is set later with SetAcceptor.
I think the change is a bit strage and convoluted but it allows one give
protocol /classes/ to the c++ constructors instead of protocol instances.
This is nice because derived classes (like HTTP) don't need to copy the
protocol instanciation code.
This might need to be changed in the future if ev is needed in thread pools
or extension libraries. However for now it makes sense to just use a single
loop.
