go.tools/cmd/godoc: add redirect helpers
go.tools/cmd/godoc: add redirect helpers

Previously these helpers were added by a private deployment script.
There's no reason why they shouldn't be part of godoc proper now
that it's in the go.tools repository.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/13722043

skyportsystems/go.tools,bryanxu/go-zh.tools,d0f/go-zh.tools,bryanxu/go-zh.tools,webfd/go-zh.tools,skyportsystems/go.tools,d0f/go-zh.tools,d0f/go-zh.tools,8limbs/gotools,webfd/go-zh.tools,skyportsystems/go.tools,skyportsystems/go.tools,8limbs/gotools,skyportsystems/go.tools,d0f/go-zh.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,webfd/go-zh.tools,d0f/go-zh.tools,8limbs/gotools,webfd/go-zh.tools,webfd/go-zh.tools