more memory-efficient implementation of line reading

fix #1409

fix #1396

add network name to RPL_WELCOME

Record INVITE in DM history for the benefit of offline always-on clients

* Defer account login snomask until after connection registration is complete
* Don't send account-notify for pre-registration clients

fix #1411

Clients without event-playback should receive client-only tags in
replayed PRIVMSG / NOTICE.

fix #1387

fix #1407

Fixes #1407

New Crowdin updates

Make atheme2json sort channel modes

This makes invoking the script multiple times with the same input return
the same result, which may not be the case before because sets are
unordered and thus the channel modes can become reordered across
multiple invocations of the script.

Allow atheme2json to handle mlock mode removal (outside of `-t` or `-n`)

For example, if the mlock is set to `-i`, `i` is not present in the
`modes` and thus it would error.

I'm inclined to think that the negative mlock feature doesn't behave
correctly, because the mlock of `-i` (or `-n`) would prevent anyone from
ever setting those modes on the channel. Which this does not appear to
be the case.

Fixes #1401

Instead of building a new serialized message for each recipient,
try to cache them.

mention UN[DK]LINE in [DK]LINE help

fix duplicated JOIN line sent to some resuming clients

Resuming clients without the resume capability would receive
two JOIN lines per channel.

docs/MANUAL.md: fix atheme2json link

add a manual entry for rehash

documentation updates for proxy v2

fix #1389

Support PROXY protocol v2, including ahead of plaintext connections

upgrade ircmsg again

upgrade ircmsg; fixes #1385

Validate tag names and values in accordance with the ratified message-tags spec

fix output bugs in AMODE handling

fix casefolding issue in NS SUSPEND DEL

NS SUSPEND DEL incorrectly required the use of the casefolded account name.

implement NS RENAME