Proposal 358 extension numbering

I read proposal 358.

I am quite doubtful that this is the right way to try to improve things. I think we should step back a bit and try to understand the goal here. Are we just trying to remove needless divergence?

Removing needless divergence is good, but I'm not sure that conflating these two handshake extensions is the best way to do that.

Also, I think that using a different protocol number for CC_REQUEST as for CC_RESPONSE is also needless divergence, and this spec change seems to entrench it.

I'm not sure exactly where to go from here in the spec language. In practical terms, my personal taste would suggest that:

• New extensions to the circuit handshake ought all to have new numbers, which are unique across all kinds of handshake
• New extensions ought to use the same number for requests and responses.

CC @nickm