ERR_error_string() is just broken, as it returns at most 119 chars
which means error messages are frequently truncated.
Allow for 511 chars using ERR_error_string_n().
This lets a user connect with a client certificate, and
passes the certificate's fingerprint to ircd, which
currently just notices it to the user.
A new ssld->ircd message 'F' is used to pass on the
fingerprint.
This is only for OpenSSL for now, not GNUTLS.
