Fix lingering Python filters on Python 2.5
Fix lingering Python filters on Python 2.5

threading.Thread doesn't have the daemon attribute on Python 2.5, so
terminating Python filters would wait indefinitely for the stdout thread
to exit.  Use the older setDaemon API to daemonize the thread.

cmusatyalab/opendiamond,cmusatyalab/opendiamond,cmusatyalab/opendiamond,cmusatyalab/opendiamond,cmusatyalab/opendiamond