go/types: include link to source in generated files
This makes navigation a little easier.
Also, make the "inconsistent generated files" test's
error message more explicit about which file is which.
Change-Id: Iae1fb9e496fb68325448d807469a5b0c55ceda99
Reviewed-on: https://go-review.googlesource.com/c/go/+/574715
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>