is_buffer -> check_buffer; fix bug improperly using newstyle buffer on oldstyle-only objects
is_buffer -> check_buffer; fix bug improperly using newstyle buffer on oldstyle-only objects

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