ircv3 support in rcirc

[William Cummings <will@wpc.io>]

Hey all,

I've been hacking up rcirc.el to support the ircv3 [1] server-time
capability. I use this to get nice backlogs from ZNC [2] :) Right now I
just have a hacked up copy of rcirc.el in my dotemacs. I'm starting to
think about how to extend rcirc to support ircv3 capabilities, so that
my code could be a cleaner extension of rcirc. Is this a patch that
would be welcome?

Here's how I imagine this working:

* v3 extensions can be implemented in separate features, for ex.
rcirc-server-time
* rcirc has a list holding a list of capabilities it will request, the
feature will append the capabilities it would like to request
* rcirc sends CAP REQ for each requested feature upon connection
* when rcirc receives a CAP ACK message, it dispatches this to the
appropriate functions/hooks, for ex rcirc-CAP-ACK-server-time or
rcirc-cap-ack-received-hook
  rcirc could maintain its own list of ack'd capabs, and hooks could do
  something like (rcirc-with-capability "server-time" ...) which would
  only execute if the capab has been ack'd by the server

* when present message tags will be parsed and provided to callbacks and
hooks
* maybe a on-connect hook? i need this to req backlog after connection
but doesnt necessarily relate to the rest here

Something along these lines would allow me (and others) to implement a
v3 extension w/o overriding functions in rcirc. Any thoughts about this
approach?

[1] http://ircv3.net/irc/
[2] http://wiki.znc.in/Playback