go/parser: disable scoping code always

Seems to be enabled spuriously during godoc (can't see why),
producing errors like:

parser.parseDir: src/pkg/http/server.go:159:16: 'Write' declared already at src/pkg/http/request.go:140:21 (and 4 more errors)

R=r
CC=golang-dev
https://golang.org/cl/194119
1 file changed