bufio: fix handling of empty tokens at end of line/file
Fixes issue 8672.

LGTM=rsc
R=golang-codereviews, rsc
CC=golang-codereviews
https://codereview.appspot.com/145390043
spec: clarify embedding of interfaces

Fixes issue 7886.

LGTM=iant, r, rsc
R=r, iant, rsc, ken
CC=golang-codereviews
https://codereview.appspot.com/149010043
spec: clarify scope and re-use of iteration variables

Fixes issue 7834.

LGTM=iant, rsc, r
R=r, rsc, iant, ken
CC=golang-codereviews
https://codereview.appspot.com/148940044
cmd/go: install dependencies for 'go build -i' on a command

Fixes issue 8242.

LGTM=r
R=golang-codereviews, r
CC=golang-codereviews, iant
https://codereview.appspot.com/147150043