Added -C username and -G username that allow a user (usually Administrator)

Added -C username and -G username that allow a user (usually Administrator)
to change the ownership or group ownership of a file to any arbitrary user
from the UNIX command line.
This will show the people who quote NT manuals at us about how this is
"impossible" how their operating system really works :-).
Jeremy.
(This used to be commit 12f88c9ba731bdded626b9d011cfc8d2ba09010e)