libgo: update to Go 1.16.2 release

Change-Id: Ic12711a34cc086df02c47888361522ad8e740261
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/301459
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
32 files changed