Completion/User functions again

["Andrej Borsenkow" <Andrej.Borsenkow@mow.siemens.ru>]

I'm still feeling uneasy about installing all of these functions. There are
several reasons:

 - _tar and _find are hopelessly GNUish. You cannot expect, that users will
study every function to find out if it is applicable to there system. They will
simply install it and wonder why it does not work. Of course, gzip, configure
etc are GNU as well - but they do not conflict with system standard commands.

 - _hosts, _rlogin, _x_options are using array hosts. This most probably does
not exist. Again, I do not like installing something that does not work
out-of-the-box by default. This should be done explicitly in hope, that users
understand what's going on :-)

 - _chown, _chgrp, _stty are too system dependent. It is better to not provide
completion at all than provide completion that only partially works. I do not
suggest removing them from distribution - but to not install them by default.

To summarise - I firmly believe, that everything that gets installed must work
"as is" on every system. Anything that works only on some systems or something
that needs additional setup should only be installed explicitly.

/andrej