Migrate from NGINX-RTMP, support IPv6 protocol.

[Winlin]

NGINX-RTMP can listen only on IPv6 ports during the listen process, refer to: https://github.com/arut/nginx-rtmp-module/wiki/Directives#listen
ipv6only=on|off

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[Winlin]

We listen at tcp4+tcp6 now: #988
But we should support more features.

[Winlin]

Already supported.

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