IPADDRESS breaking change, empty eval changed

[tablatronix]

    IPAddress     thisisanipaddress;
    if(thisisanipaddress){Serial.println("YARP);}  // WAS NARP until ipv6 pr maybe..

Any code checking an unset or NULL ip address will no longer evaluate to false.

various changes to ipaddress.cpp, I am assuming from dword 0, to struct via IP_ANY_TYPE (&ip_addr_any_type) at cursory glance.