The plan for godoc:
- Copy godoc source from the core repo to go.tools (this CL).
- Break godoc into several packages inside go.tools, leaving a package
main that merely sets up a local file system, interprets the command
line, and otherwise delegates the heavy-lifting to the new packages.
- Remove godoc from the core repo.
- Update cmd/go to install this godoc binary in $GOROOT/bin.
- Update misc/dist to include godoc when building binary distributions.
R=bradfitz
CC=golang-dev
https://golang.org/cl/11408043
