C: add Michael Piatek (Google CLA).

R=golang-dev, r
CC=golang-dev, piatek
https://codereview.appspot.com/14681043
net/http: skip content-type sniffing if the header is explicitly unset.

Fixes issue 5953

R=dsymonds, bradfitz, rsc
CC=golang-dev
https://codereview.appspot.com/14434044

Committer: David Symonds <dsymonds@golang.org>
cmd/gc: fix comment about performing indexing at compile time.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/14441070