net/http: fix a panic in Redirect

R=golang-dev, dsymonds, r
CC=golang-dev
https://codereview.appspot.com/8721045
sort: don't depend on math

No reason to pull in math just for x != x.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/8886043
api: update next.txt; add io.ErrNoProgress

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/8887043