Chunk messages that are larger than the IRC line length limit

[LeftyBC]

We should be able to determine the IRC line length limit and chunk messages that, when encrypted+encoded, are larger than that limit.

[johnmaguire]

Just FYI, when implementing this in an IRC bot I wrote I learned the hard way that the limit for one user is different than another use. If the IRC server is following RFC 2812, it should allow 512 chars (subtract 2 for CRLF and you've got 510) per line. But a line includes prefix, hostname, ident, channel, etc. So it can be tricky to take all the diff variables into account. I think we settled on 200 after looking at the possible max values for all the other variables, but it's definitely possible to be smarter about it (though possibly painful.)