SPDY support

[mikeal]

SPDY is going in to wider use and we'd like to support it but we use stud as our TLS terminator.

I'm trying to find a good support strategy and I was thinking this might work:

--spdy option.

Do proper TLS Next Protocol Negotiation to support SPDY.

The first byte of each new TCP connection could indicate if this is a SPDY connection or not, similar to how --write-ip works so that I can route to a server that parses regular HTTP or SPDY (I'll have to route to an entirely seperate server because there is no NPN indicator to flip from HTTP to SPDY on the plain TCP side so I'll have to split between SPDY and HTTP servers).