2012.07.10 Version 0.6.20 (maintenance)

* npm: Upgrade to 1.1.37 (isaacs)

* benchmark: Backport improvements made in master (isaacs)

* build: always link with -lz (Trent Mick)

* core: use proper #include directives (Ben Noordhuis)

* cluster: don't silently drop messages when the write queue gets big (Bert Belder)

* windows: don't print error when GetConsoleTitleW returns an empty string (Bert Belder)