Client side version negotiation rewrite

Continuing from the previous commit this changes the way we do client side
version negotiation. Similarly all of the s23* "up front" state machine code
has been avoided and again things now work much the same way as they already
did for DTLS, i.e. we just do most of the work in the
ssl3_get_server_hello() function.

Reviewed-by: Kurt Roeckx <kurt@openssl.org>