[Bro] Event for syn-ack packet

[Vern Paxson]

> Ok, my confusion was that the comment for that event in event.bif was "The event is raised when the initial 3-way TCP handshake has successfully finished for a connection."

Yeah, I think you can pin the blame on me for that comment.

> I'll update that comment unless there's some other subtlety about why it's worded that way.

Updating it would be good.

> One caveat could still be that connection_established is TCP-specific, the example I gave could be used for UDP "connections", too.

I don't believe we generate connection_established in a UDP context.  There
it's instead udp_request and udp_reply.  I'm not sure what example you're
referring to.

		Vern