go/loader: resolve imports in "created" packages w.r.t. parent dir not cwd

Fixes golang/go#16580

Change-Id: Id891f40659257eac9dbb0d70dae17f725e911f9b
Reviewed-on: https://go-review.googlesource.com/33589
Reviewed-by: Robert Griesemer <gri@golang.org>
2 files changed