simplify semaphore release code

fix #1592

Implements the new `CHATHISTORY LISTCORRESPONDENTS` API.

try to record buntdb errors from persisting lastSeen

Potentially fixes the database corruption seen on #1603

See #1603

fix #1594

fix #1576

1. Use FAIL instead of WARN
2. Use NICKNAME_RESERVED instead of ACCOUNT_REQUIRED
3. Don't send 433 at all for registered clients, just send the FAIL

List IRCv3 CAPs in `NS CLIENTS LIST` output

Send a WARN NICK ACCOUNT_REQUIRED on attempt to take a reserved nick

fix #1596

All truncation must be made UTF8-safe.

fix #1531

Fix #1562

AWAY status should be tracked per-session:

1. With auto-away enabled, away status is aggregated across sessions
   (if any session is not away, the client is not away, else use
   the away status that was set most recently)
2. With auto-away disabled, we get the legacy behavior where AWAY
   applies directly to the client

Implement the new bot mode spec:
https://github.com/ircv3/ircv3-specifications/pull/439

some small fixes/enhancements

RELAYMSG should respect mutes

Improve error message for CS TRANSFER

PerstentStatusMandatory should display as "enabled", not "mandatory",
in the context where it refers to a user-chosen setting.

Allow chanops to delete channel messages from history

Handle panics in rehash, even if it was triggered by SIGHUP

bump irc-go again

Fix link to productionizing guide.

bump irctest

deprecate message truncation

Implements #1577, but the issue should remain open until we clean up
the debugging loglines.

fix #1584

See #1584

Send 477 ERR_NEEDREGGEDNICK when an unregistered user messages a +R user.

Minor documentation updates.

docs/MANUAL.md: add recommendation for proxy timeout

The +M channel mode is documented twice. Merge the two sections.
Clarify that +R restricts both joining and speaking, but does not kick existing unregistered users.

Fixes #1064.