* Mark test helpers and test-only specs as cfg(test)
* Use test-probe to conditionally compile test helpers
* Remove test probe and directly use features tag
* Alter IO queueing.
* Don't require IoMessages to be Clone
* Ancient blocks imported via IoChannel.
* Get rid of private transactions io message.
* Get rid of deadlock and fix disconnected handler.
* Revert to old disconnect condition.
* Fix tests.
* Fix deadlock.
