Initial support

tested against OpenSSL 1.0.1, 1.0.2, 1.1.0, Yassl and LibreSSL
not working on Windows with native SChannel support, due to wrong cipher
mapping: Latter one requires push of CONC-241 fixes.
Please note that OpenSSL 0.9.8 and OpenSSL 1.1.0 will not work: Even if
the build succeeds, test cases will fail with various errors, especially
when using different tls libraries or versions for client and server.