work in SSLv3: initial handshake has no extensions but includes MCSV, if
server indicates RI support then renegotiation handshakes include RI.
NB: current MCSV value is bogus for testing only, will be updated when we
have an official value.
Change mismatch alerts to handshake_failure as required by spec.
Also have some debugging fprintfs so we can clearly see what is going on
if OPENSSL_RI_DEBUG is set.
