SHUT_RDWR: Define as a dummy macro.

It is not available on lwIP version 1.3.x
TCPServer#initialize: Add workaround for AI_PASSIVE.

There will be no AI_PASSIVE macro in some IP protocol stack for embedded systems (like lwIP version1.3.x).
So there also will be no AI_PASSIVE constant in Socket class.
In almost all protocol stacks, they will have only IPv4.