more fine-grained error reporting (`Fail with different constructors)

(console output from mirage-client:)
read 159 certificates, could validate 104
verify server certificate Google Internet Authority G2 -> www.google.com
successfully verified server certificate
verify certificate GeoTrust Global CA -> Google Internet Authority G2
looking for issuer of GeoTrust Global CA (104 CAs)
verify certificate NO commonName 58ce29eafcf7deb5ce02b917b585d1b9e3e095cc25310d00a6926e7fb692639e5095d19a6fe411de63856e98eea8ff5ac8d355b2667157dec021eb3d2aa72349010486427bfcee7fa21652b56767d340db3b2658b228773dae147761d6fa2a6627a00dfaa7735cea70f1942165445ffafcef2968a9a28779ef79ef4fac077738 -> GeoTrust Global CA
HANDLE_RECORD (in state Shaking hands) HANDSHAKE
some output