doImport is itself a thin wrapper around Import, and doPkg is its only call
site. I'm having trouble following what doPkg is doing due to the indirection,
so I'm removing it.

Change-Id: I6167be68e869a36010a56a5869df50b1145ac813
Reviewed-on: https://go-review.googlesource.com/125837
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>