Tolerate disappearance of named bug-workaround bits,

without invalidating user configurations.  Just redefine the bit's
value as zero.  SSL_OP_MSIE_SSLV2_RSA_PADDING has been re-cycled as
SSL_OP_SAFARI_ECDHE_ECDSA_BUG.  Always ignore the latter, it is not
relevant with SMTP.