OpenSSL TACK patch by Trevor Perrin.

This patch enables the SSL server to respond with a TACK_Extension.  The
TACK_Extension is set via the new "SSL_CTX_use_tack_files" command.

The "openssl s_server" command can be used to run a TACK test server, using
its new -tack, -tackbreak, and -activation_flags arguments.

For example, if you have tlslite installed in ~/tlslite, you can run a test server with:

openssl s_server -accept 4443 \
  -cert ~/tlslite/tests/serverX509Cert.pem \
  -key ~/tlslite/tests/serverX509Key.pem  \
  -tack ~/tlslite/tests/TACKs.pem \
  -activation_flags 3

Then contact it with:

tls.py client localhost:4443