#236 SSDP not working reliably on Mac OS X Mavericks

[Steven Blackburn]

Having issues with minidlna not advertising itself reliably - usually resulting in the following error in the log:
error: setsockopt(udp, IP_ADD_MEMBERSHIP): Can't assign requested address

I noticed that imr_address is not set up when ip_mreqn is used. Setting that to the interface address appears to resolve the problem. It could probably be initialised to some "use sensible value" - the issue is likely with it being uninitialised and so containing garbage in my setup. NB: In case it makes a difference, this is compiling with Xcode / macports.

I've attached a git patch that works for me.