Remove need for spoon, since RSA will fails gracefully.
Add support for full private key format for fast decryption.
Generalization of key exchange to add future support for DH, etc.
despite the fact that it works, it's missing a step at key block set time,
so that we don't use the computed IV, but use a random generated one seeded by
the computed IV.
the API stays mostly similar except for clientkeyxchg that need a bytes instead of [word8].
remove lots of unnessary packing/unpacking when setting up ciphers.
