Merge pull request #765 from pijyoi/master

make win32 signaler support ephemeral ports
Fix issue #763
Merge pull request #766 from hurtonm/master

Fix issue #763
changing zmq_proxy_steerable to not use null terminated strings
Merge pull request #768 from Talksum/master

changing zmq_proxy_steerable to not use null terminated strings
Code cleanup
Merge pull request #770 from hurtonm/master

Code cleanup
use enum retired_fd instead of -1

using -1 causes a warning on Windows platform because SOCKET is unsigned.