cmd/guru: add workaround to handle inconsistency between go/types and gc

Add identical workaround from gorename to guru. Only affects queries
that typecheck the code first.

Fixes golang/go#16530

Change-Id: I718cfceb8d26868eea9128c8873b164333c50f53
Reviewed-on: https://go-review.googlesource.com/33359
Reviewed-by: Alan Donovan <adonovan@google.com>
10 files changed