DAQ GDS broadcasters need to use different frameXmitPorts

At LLO, we have had dual GDS broadcasters working during O3 and before. This works by having them transmit UDP packets on different VLANs (GDS0 on 10.103.255.255, GDS1 on 10.105.255.255), with each DMT machine equipped with two Ethernet ports for this. This is configurable with the daqdrc file. However, the DMT user want these to also use separate IPs. The normal values are

framexmittypes.hh:   const int 		frameXmitPort = 7096;
net_writer.hh:  static const int concentrator_broadcast_port = diag::frameXmitPort + 1;
net_writer.hh:  static const int concentrator_broadcast_port_tp = diag::frameXmitPort + 2;
net_writer.cc:    printf("WARNING: DMT broadcaster opened on non-standard port %d\n", diag::frameXmitPort + 2);
net_writer.cc:    if (!radio.open (istr, mcast_interface, diag::frameXmitPort)) {

However a special version of daqd was built on GDS1 that has a change to net_writer.cc

net_writer.cc:     printf("WARNING: DMT broadcaster opened on non-standard port %d\n", diag::frameXmitPort + 3);
net_writer.cc     if (!radio.open (istr, mcast_interface, (diag::frameXmitPort+3))) {

Ignoring the comment, it appears GDS0 uses 7096, GDS1 uses 7099

This should be built into the DAQ code as a parameter -- We have a test DMT computer set up on the large DAQ test stand to enable testing this