OTRv4 implementation

by Max for Xelerance Corporation

Since I do not have in-depth knowledge of OTR internals yet and I do not want to just copy-paste description from xelerance.com I'll try to make brief description as I understood it so far. The basic idea is to implement OTRv4 feature for creation (and secure transfer) of temporary symmetric cryptographic keys which can be used to securely transmit large amount of date (voice & video streams, file transfer) between OTR clients.