Added cmode +A (Auditorium mode).
When a channel is in auditorium mode, users can only see ops/voiced users on the channel and messages that are sent to the channel by non-ops/voiced users are being relayed to #channel-relay. Ops and voiced users can see the full user list.

Also, joins/parts/quits of non-ops/voiced users are only sent to ops/voiced users.

This channel mode is intended for network-wide events and currently can only be set by u:lined servers (services).

-Kobi.