Handle CALLBACK_API retirement.
Handle CALLBACK_API retirement.

JlnWntr/usrsctp,CoolmanCZ/usrsctp,sctplab/usrsctp,liamstask/usrsctp,JlnWntr/usrsctp,sukinull/usrsctp,saghul/usrsctp,bebo/usrsctp,weinrank/usrsctp,ossy-szeged/usrsctp,liamstask/usrsctp,sctplab/usrsctp,weinrank/usrsctp,CoolmanCZ/usrsctp,sukinull/usrsctp,bebo/usrsctp,saghul/usrsctp,faithfracture/usrsctp,ossy-szeged/usrsctp,faithfracture/usrsctp,JlnWntr/usrsctp,CoolmanCZ/usrsctp,sctplab/usrsctp,CoolmanCZ/usrsctp,faithfracture/usrsctp,weinrank/usrsctp