Add regress coverage for tls_peer_cert_common_name()

Remove the ability to do tls 1.0 and 1.1 from libtls.

With this change any requests from configurations to request
versions of tls before tls 1.2 will use tls 1.2. This prepares
us to deprecate tls

Remove the ability to do tls 1.0 and 1.1 from libtls.

With this change any requests from configurations to request
versions of tls before tls 1.2 will use tls 1.2. This prepares
us to deprecate tls 1.0 and tls 1.1 support from libssl.

ok tb@

show more ...

Use a larger (2048 bit) RSA test key.

Otherwise we fail to do PSS signatures since the key size is too small.

Update protocol version test to include TLSv1.3.

Add tls_conn_cipher_strength() to gotls regress.

Add a test that covers a libtls client talking to a Go TLS server with
varying minimum and maximum protocol versions. This gives us protocol
version test coverage against an independent TLS stack.

Add handling for errors on the TLS config and properly check/handle
failures when setting the CA file.

Single byte read/write tests.

Add test coverage for peer certificate info and connection info.

Now that tls_close() is more robust, consider a failure to be fatal.

Update regress for the libressl to libtls rename.