fixed daemon support for Linux

Hi!

I finally fixed the daemon support for linux. The problem was, if you
started the PyDS over a ssh connection on a remote machine, the ssh
connection didn't close correctly afterwars, as the daemon still was
attached to your terminal session. You needed to forcebly close the ssh
connection.

I fixed this by using a much better become_daemon implementation that both
does the double-fork trick and correctly disconnects the stdin/stdout/stderr
filehandles.

I did some restructuring of the PyDS.Daemonize module, so it would be great
if one of you windows users could try the current CVS version, wether it
behaves correctly!

bye, Georg