Fix handshaking properly. Also, fix ID syncup. It now will completely freeze the idmap after preinit.
This frozen map is used to inject "new" stuff into existing serverside worlds. Interesting sideeffect: remote
servers lacking things will change the client, to also LACK ids for those things. watch for -1 ids in your remap
events. Note: idmaps should be considered temporary per server instance. SERVERSTOPPED will restore "startup" state,
as will client logout.