This patch adds support for the OTR protocol to irssi. This is an import
of the external irssi-otr project that we are now taking over
maintership for.
Major thanks to the original authors of Irssi-OTR: Uli Meis and David
Goulet. Thanks to the OTR community in #OTR on OFTC, thanks to everyone
who have helped testing the patches and submitted UI suggestions.
