sys.exit handling by script/driver

The code in the $prefix/scripts/driver script concedes
that it is valid for a script it is supervising to exit using
the sys.exit function rather than just returning from the
main function.

However, if the script being supervised does use
sys.exit, the driver script fails to pass on the output
generated by the supervised script.

In the case of cgi scripts this means that an internal
server error is reported by the http server because no
output has been returned.

A patch file to fix this problem is available as #668685

[http://sourceforge.net/tracker/index.php?func=detail&aid=716754&group_id=103&atid=100103]