Add code to handle change of cipher state in the new TLSv1.2 record layer.

Add code to handle change of cipher state in the new TLSv1.2 record layer.

This provides the basic framework for handling change of cipher state in
the new TLSv1.2 record layer, creating new record protection. In the DTLS
case we retain the previous write record protection and can switch back to
it when retransmitting. This will allow the record layer to start owning
sequence numbers and encryption/decryption state.

ok inoguchi@ tb@