HTTP/1.0 does not mandate a Content-Length header in responses since keep-alive connections aren't a thing; the connection closure then signals the end of the response.
This change requires the URL metadata line for processing HTTP/1.0 data, so it plays well with `warc-dump-responses --meta`.

Just catching the BrokenPipeError is not sufficient. There might still be data in the stdout buffer, which then causes the following error when Python shuts down and flushes it:

	Exception ignored in: <_io.TextIOWrapper name='<stdout>' mode='w' encoding='utf-8'>
	BrokenPipeError: [Errno 32] Broken pipe

To handle this, redirect stdout to /dev/null in the exception handler before exiting: https://docs.python.org/3.11/library/signal.html#note-on-sigpipe

%n takes a signed int so is incompatible with size_t; further, sscanf could in theory return a negative value (EOF).