imports: properly handle global variables when creating imports

Fixes golang/go#7463

Change-Id: Ib8b511a34c562a2b3cdce6bb143caa7cf453bd00
Reviewed-on: https://go-review.googlesource.com/23444
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
2 files changed