like this: "CAP REQ :capability1 capability2 capability3" for example.
References:
- - <http://ircv3.atheme.org/specification/capability-negotiation-3.1>
+ - <http://ircv3.net/specs/core/capability-negotiation-3.1.html>
- <http://ngircd.barton.de/doc/Capabilities.txt>
- doc/Capabilities.txt