Support using ipv6 in make_client/make_server method

[cocolato]

Fix: #204

[aisk]

There are still some codes where socket_family is applied to unix domain sockets.

[cocolato]

There are still some codes where socket_family is applied to unix domain sockets.

Does this mean that when users pass in the unix_socket option, they will not be supported to pass in the additional socket_family option?

[aisk]

Yes, the unix domain socket's socket_family must be AF_UNIX. See: https://www.ibm.com/docs/en/i/7.3?topic=characteristics-socket-address-family

[cocolato]

Yes, the unix domain socket's socket_family must be AF_UNIX. See: https://www.ibm.com/docs/en/i/7.3?topic=characteristics-socket-address-family

Updated.

[aisk]

I only have one suggestion left, otherwise this change looks good to me.