How to Handle IRC Bouncer Timestamps

[lkiesow]

The protocol definition should also be ablte to handle timestanps like they are often attached to messages in baclogs generated by IRC bouncers like ZNC. The handling of such timestamps should be optional—thus a client can be called IRCrypt compliant even if it does not support this—as the majority of users probably does not need this. But it is still a good idea to define a proper way of handling such things.