allow m_messageflood to do something more useful than kick users

[kaniini]

So I use an inspircd network and sometimes the server kicks me because of flooding, which then has a painful intersection with +J (or as I lovingly call it "twat mode").

It seems to be a common pain point, so I was thinking, instead of kicking people for flooding which is intrusive anyway... why not just block their messages after the configured threshold? Most intersections with +f are not from bots, but legitimate participants, especially if it's misconfigured.

@SaberUK was talking about this the other day, I think. Also I noticed #499 but it seems like a dead issue, so I opened this one up.

[HelixSpiral]

Pull #471 allows for blocking instead of kick(ban)ing. I know we discussed that on IRC, just referencing it here for anyone reading this issue.