Merge branch 'js/win-kill-child-more-gently'

Advanced emulation of kill() used on Windows in GfW has been
upstreamed to improve the symptoms like left-behind .lock files and
that fails to let the child clean-up itself when it gets killed.

* js/win-kill-child-more-gently:
  mingw: really handle SIGINT
  mingw: kill child processes in a gentler way