some minor cleanups to the fdset code
some minor cleanups to the fdset code

m13253/pycurl-python3,ninemoreminutes/pycurl,m13253/pycurl-python3,ninemoreminutes/pycurl,m13253/pycurl-python3,jcharum/pycurl,ninemoreminutes/pycurl,jcharum/pycurl,jcharum/pycurl,ninemoreminutes/pycurl