+TCP multi static and ARP issues

Libraries
21

Also adding, mDNS needs to explicitly set the endpoint somewhere, weighting the prvFillSockAddress to choose up interfaces results yields an empty endpoint, requiring adding

        if( pxEndPoint != NULL )
        {
            xDNSSocket->pxEndPoint = pxEndPoint;

in prvGetHostByNameOp

22

@htibosch Do you have any suggestion here?