Fix detection of loopback addresses.
Fix detection of loopback addresses.

This fixes https://github.com/sctplab/usrsctp/issues/51.

faithfracture/usrsctp,sctplab/usrsctp,weinrank/usrsctp,weinrank/usrsctp,CoolmanCZ/usrsctp,CoolmanCZ/usrsctp,CoolmanCZ/usrsctp,JlnWntr/usrsctp,sctplab/usrsctp,sctplab/usrsctp,faithfracture/usrsctp,weinrank/usrsctp,JlnWntr/usrsctp,CoolmanCZ/usrsctp,faithfracture/usrsctp,JlnWntr/usrsctp