go/build: add dependency test
This exercises the Import function but more importantly
gives us a place to write down the policy for dependencies
within the Go tree. It also forces us to look at the dependencies,
which may lead to adjustments.
Surprises:
- go/doc imports text/template, for HTMLEscape (could fix)
- it is impossible to use math/big without fmt (unfixable)
- it is impossible to use crypto/rand without math/big (unfixable)
R=golang-dev, bradfitz, gri, r
CC=golang-dev
https://golang.org/cl/
5732062