Add basic support for TLS 1.2, from operasoftware fork.

Forward-ported from changes by Yngve N. Pettersen, Opera Software ASA,
from https://github.com/operasoftware/tlslite
Enable TLS 1.2 as maxVersion.

Forward-ported from changes by Yngve N. Pettersen, Opera Software ASA,
from https://github.com/operasoftware/tlslite
Add support for new TLS1.2 cipher suites (RSA+SHA256).

Forward-ported from changes by Yngve N. Pettersen, Opera Software ASA,
from https://github.com/operasoftware/tlslite
CertificateRequest: Update for changes in TLS 1.2.

Forward-ported from changes by Yngve N. Pettersen, Opera Software ASA,
from https://github.com/operasoftware/tlslite
README: Add acknowledgement for Yngve N. Pettersen (TLS 1.2 support).