Add support for Unix domain sockets.

This ensures that host:port is used rather than an empty address,
which defaults to 127.0.0.1:3306 (ignoring the host in the config).

This adds a new configuration option, socket-path, instead of using
host.

Revert "Add support for Unix domain sockets"

#1011: recommend allowing webirc from localhost

Add support for Unix domain sockets

make histserv replies come from histserv, not hostserv

fix #1005

fix #858 and #383

fix #1003

upgrade go-ident to fix parsing issue

ratify SETNAME

fix #996

treat channel founder as such even if they don't have +q

Call ApplyUserModeChanges for default user modes.

This ensures that counts like the number of invisible users are updated
correctly.

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

As of 3dc5c8de78, the PROXY-before-TLS proxy line
and any proxy information carried in X-Forwarded-For
do not count as the "first line", so an additional
client-supplied PROXY line would have been accepted.

fix #994

fix #952

Hide +i users from WHO * queries.

Construct a hash set of the user's channels and check that rather than
querying channel membership, to reduce the number of locks that need to be
acquired.

simplify listener rehash logic

new recommended default: proxy allowed from localhost

use 8097 as the example websocket port

Fixes #990.