go/parser: use non-adjusted position while parsing CommentGroups
Line directives should not affect the way Comments get grouped
into CommentGroups.
Change-Id: I9aa4b558cb1333b32be692e8720291d0e6961cae
GitHub-Last-Rev:
de867b27bff28983716ba9126329d75f456a2b5a
GitHub-Pull-Request: golang/go#69133
Reviewed-on: https://go-review.googlesource.com/c/go/+/609515
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>