Minor changes to ioloop.py.
Minor changes to ioloop.py.

dash-dash/pyzmq,dash-dash/pyzmq,ArvinPan/pyzmq,swn1/pyzmq,Mustard-Systems-Ltd/pyzmq,caidongyun/pyzmq,ArvinPan/pyzmq,dash-dash/pyzmq,yyt030/pyzmq,caidongyun/pyzmq,ArvinPan/pyzmq,swn1/pyzmq,yyt030/pyzmq,caidongyun/pyzmq,yyt030/pyzmq,swn1/pyzmq,Mustard-Systems-Ltd/pyzmq,Mustard-Systems-Ltd/pyzmq