Banner at the top of godoc.org pages are already asking users to
redirect to pkg.go.dev as mentioned in blog post
https://blog.golang.org/pkg.go.dev-2020
Signed-off-by: Andrew Hsu <xuzuan@gmail.com>
Update license header to standard format for source files missed prior.
Add license header to new source files.
Add Makefile check to test all `*.go` and `*.sh` files have a copyright
notice (or comment about them being auto-generated) within the first few
lines.
