Re: p1: Upgrade ordering (possible HTTP/2 impact)

I suggest the following change, since otherwise it could be understood that the server may return the protocols in any
order instead of in order of relative preference in a 101 response:

"A server MUST send an Upgrade header field in 101 
(Switching Protocols) responses to indicate which 
protocol(s) are being switched to, in order of relative preference,
and MUST send it in 426 (Upgrade Required) responses [etc]."

--Peter