handle certificates with RSA-PSS signature that have RSAk public keys

[JacobBarthelmeh]

Description

RSAk CA signing a RSAk pub key cert with RSA-PSS signature.

$ ./examples/server/server -c ./certs/rsapss/server-mix-rsapss-cert.pem -k ./certs/server-key.pem -A ./certs/rsapss/client-rsapss.pem -V

$ ./examples/client/client -A ./certs/ca-cert.pem -C -c ./certs/rsapss/client-rsapss.pem -k ./certs/rsapss/client-rsapss-priv.pem