Listen 0.0.0.0 only on IPv4

[lifenjoiner]

For

dnscrypt-proxy/dnscrypt-proxy/example-dnscrypt-proxy.toml

Lines 39 to 40 in f5912d7

	## To listen to all IPv4 addresses, use `listen_addresses = ['0.0.0.0:53']`
	## To listen to all IPv4+IPv6 addresses, use `listen_addresses = ['[::]:53']`

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

[lifenjoiner]

Or change the comments instead?

[jedisct1]

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.

[lifenjoiner]

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.