Add new failing read/signal test

Add new failing read/signal test

^C does not abort `read < /dev/zero', instead it read(2)s indefinitely,
one null byte at a time;  bash and ksh93 from ports abort as expected.

Use the new timeout(1) $PROG trick to send ^C after 0.1s, but also
rely on it's -k for the final SIGKILL to stop the busy-looping process.

./th's `time-limit: 1' prints "test timed out (limit of 1 seconds)" but
leaves the process running.