GitLab

Also throw in a few more shift constant folding.

Change-Id: Iabe00596987f594e0686fbac3d76376d94612340
Reviewed-on: https://go-review.googlesource.com/19543


Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>