remove crufty hacks around irc crate

[eeeeeta]

We currently do a whole bunch of annoying stuff to work around limitations in the irc crate. This should either be upstreamed, or moved into its own module. Non-exhaustive list:

• ideally the client should autoidentify, I don't know why it doesn't do this already?
• we need to delay message sending until we're connected and identified, otherwise stuff gets dropped on the floor
• nick changes aren't tracked properly by the irc crate :/