Socket-based NativeBufferEvent that reads and writes data onto a network

Property definitions

libevent $ NativeBufferEvent :: socket
	# Socket-based `NativeBufferEvent` that reads and writes data onto a network
	new socket(base: NativeEventBase, fd, options: Int) `{
		return bufferevent_socket_new(base, fd, options);
	`}
lib/libevent/libevent.nit:344,2--347,3