Polipo Portability Enhancements

by chrisd for The Electronic Frontier Foundation/The Tor Project

Adapting Polipo to depend upon the libevent library, making use of its event loop, asynchronous DNS resolver and utility library, will allow us to simplify Polipo, while increasing maintainability and portability in the process. Polipo's behavior on Windows should be improved by adding support for the Windows registry to learn key path names, and by adding a launcher to run in the systray, providing the user with options to control the server.