1. TAGMSG were incorrectly being considered multilines, because
   Is512() was checking the wrong thing
2. Playback of TAGMSG should depend on event-playback, not on message-tags

This affects /TOPIC, /INVITE, and a few others.

This propagates CS AMODE changes to the actual modes, but not the other
way around.

Also fixes #909.

also, handle nickname targets in znc.in/playback

Explicit quit and ping timeout behave the same way,
but reattach after abandoning/losing the previous session
(without the break being detected server-side) is more aggressive
about replaying missed messages, at the cost of potential duplication.

Also add +C no-ctcp mode, since it's not conflicted

* Fix #684
* Fix #683
* Add `CHANSERV CLEAR`
* Allow mode changes from channel founders even when they aren't joined
* Operators with the chanreg capability are exempt from max-channels-per-account
* Small fixes and cleanup

* Fix #679 (borked reply to `JOIN #chan,\r\n`)
* Replace invalid error parameters with *'s in various places
* Fix PART with no message sending an empty trailing parameter to the channel
* Fix some error responses not getting labeled

Also ensure that people can remove their own persistent modes via CS AMODE