cmd/godoc: don't link unexported identifiers
cmd/godoc: don't link unexported identifiers

R=golang-dev, gri, gri
CC=golang-dev
https://codereview.appspot.com/9722045

Committer: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>

gnanderson/go,gnanderson/go,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,apparentlymart/golang,pombredanne/go-deleteme,apparentlymart/golang,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,gnanderson/go,tv42/old-go,gnanderson/go,gnanderson/go,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,gnanderson/go,tv42/old-go,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme