Fix reliance on irssi's ban list syncing

[eridius]

Currently bans still won't show up if they happen before irssi's ban list syncs. Irssi redirects events for the ban list sync, so we really should be able to work around this and display bans before (or even during) the sync, and we should be able to pay attention to the sync for the purposes of maintaining our internal ban list (if we care about that).

krg says caching banlist isn't useful because netsplits can get it out of sync - does irssi handle this? Caching makes this easier anyway.

[timothy]

This is no longer valid, since we don't use Irssi.