set.Of(1, 2, 3) is prettier than set.SetOf([]int{1, 2, 3}).
I was going to change the signature of SetOf but then I noticed its
name has stutter anyway, so I kept it for compatibility. People can
prefer to use set.Of for new code or slowly migrate.
Also add a lazy Make method, which I often find myself wanting,
without having to resort to uglier mak.Set(&set, k, struct{}{}).
Updates #cleanup
Change-Id: Ic6f3870115334efcbd65e79c437de2ad3edb7625
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
1a963342c7