net/http: fix when server deadlines get extended

Deadlines should be extended at the beginning of
a request, not at the beginning of a connection.

Fixes issue 4676

R=golang-dev, fullung, patrick.allen.higgins, adg
CC=golang-dev
https://codereview.appspot.com/7220076
syscall: regenerate ztype files for linux

This CL adds TCPInfo struct to linux/386,arm.
It's already added to linux/amd64.

Note that not sure the reason but cgo godefs w/ latest gcc
translates a flexible array member in structures correctly,
handles it as a non-incomplete, non-opaque type, on Go 1.
This CL reverts such changes by hand for the Go 1 contract.

R=minux.ma, bradfitz, rsc
CC=golang-dev
https://codereview.appspot.com/7197046
net/http: add Next Protocol Negotation upgrade support to the Server

This provides the mechanism to connect SPDY support to the http
package, without pulling SPDY into the standard library.

R=rsc, agl, mikioh.mikioh
CC=golang-dev
https://codereview.appspot.com/7287045