Listen `0.0.0.0` only on IPv4

For https://github.com/DNSCrypt/dnscrypt-proxy/blob/f5912d7ca99cd30213e89e865bee5da3e8c88266/dnscrypt-proxy/example-dnscrypt-proxy.toml#L39-L40

Maybe golang's behavior on this had changed some time ago. Currently, listen to 0.0.0.0 will be on both IPv4 and IPv6 interfaces, the same as ::. https://github.com/golang/go/blob/9b4b3e5acca2dabe107fa2c3ed963097d78a4562/src/net/ipsock_posix.go#L129

Or change the comments instead?

Is this not relevant any more?

0.0.0.0 should listen only to IPv4, this is the original behavior and what most people would expect.

Didn't get any response, I guess you are expecting some better solution. Frankly, my patch is not elegant, just simple and works, together with the context. I don't get a more concise one. A wrapper should be common enough. That will be complicated and indirect. If you don't opposite. I will solve the conflict and merge.