I will merge it, but I will enclose it in defines to be sure it is enabled in the kernel, like:
``` #if defined(IP_FREEBIND) ... ```
Then I will add a config parameter to turn it on, because this can create problems when having typos in `listen` parameters, so kamailio starts but doesn't listen on proper ip address. People should be aware when enabling this feature that they have to be very careful with listen ip addresses.