implement candidate compromise proposal for websockets
1. Text and binary frames are accepted
2. Text frames are sent by default
3. Binary frames are sent to clients who negotiate `binary.ircv3.net`
4. Non-UTF8 data is not accepted (enabling websockets still enables UTFONLY)
checkAlwaysOnExpirationNoMutex was respecting registered status, but
always-on clients were not considered registered at the time of the
initial check, so they were being created regardless of expiration.
INVITE playback (#1409) was buggy, due to the double use of (Item).Params[0]
for the channel name and the recipient nick. Stuff the channel name in
(Item).Message.Message instead.
Tor listeners should never see an STS cap.
Add an undocumented 'hide-sts' key for listeners that hides the STS cap.
This can be used if the listener is secured at layer 3 or 4 (VPNs,
E2E mixnets). It will be necessary to add the relevant IPs to `secure-nets`.
Store the channel-user modes of always-on clients along with their
channel memberships, restore them on server startup. This will coexist
alongside /CS AMODE, which autoapplies modes to clients on join regardless
of their always-on status.
CLIENTS LIST shows information about clients attached to a nick.
CLIENTS LOGOUT allows individual (or all) sessions to be logged out.
SESSIONS is now an alias for CLIENTS LIST.
Fixes #1072.