some validation for starters (but we actually do not want everything in here)
style
re-add lost in translation fragment
add parse_change_cipher_spec function
use parse_change_cipher_spec
server hello shouldn't contain any extension which is not sent by client hello
fix: filter renegotiation ciphersuite out of client hello (otherwise since it's kex/hash/enc is null, fails)
remove superfluous case which actually did not check correctly for secure rekeying
carry around client_hello to verify the extensions of a server hello
style
move alert level checking to reader
style
use error monad instead of exceptions
adjust tests to validation of alerts
augment List_set
de-monadify packet validation

as a bonus, keep set-like operations in one place
simplify
Merge pull request #101 from mirleft/packet-validation

Packet validation
Merge pull request #102 from mirleft/packet-validation-b

Packet validation b
remove config frontends from engine