Move the RSA-PSS check for TLSv1.3 to ssl_sigalg_pkey_ok().

Move the RSA-PSS check for TLSv1.3 to ssl_sigalg_pkey_ok().

Also, rather than passing in a check_curve flag, pass in the SSL * and
handle version checks internally to ssl_sigalg_pkey_ok(), simplifying
the callers.

ok inoguchi@ tb@