cmd/go: be clear that import loops are bad
cmd/go: be clear that import loops are bad

There was mail on golang-nuts a few weeks ago
from someone who understood the message perfectly
and knew he had a cyclic dependency but assumed
that Go, like Python or Java, was supposed to handle it.

R=golang-dev, bradfitz, dave
CC=golang-dev
http://codereview.appspot.com/6488069
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go