Add constant for PAD parameter and some cleanup.
Add constant for PAD parameter and some cleanup.

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