Improve ctrl-c handling
Improve ctrl-c handling

We don't detach the downloader process from TTY, so it receives
SIGINT as well, and may even exit sooner than Python raises
KeyboardInterrupt in the parent process.

- downloader: don't print ctrl-c traceback
- parent: handle EINTR and EOF as ctrl-c

Distrotech/urlgrabber,tradej/urlgrabber,Distrotech/urlgrabber,tradej/urlgrabber,tradej/urlgrabber,henrysher/urlgrabber,Distrotech/urlgrabber,henrysher/urlgrabber,henrysher/urlgrabber,oe-lite/urlgrabber,oe-lite/urlgrabber,oe-lite/urlgrabber,henrysher/urlgrabber,oe-lite/urlgrabber,Distrotech/urlgrabber