add the documented in the manual but not implemented variable
expansions.
From: Christos Zoulas <christos@deshaw.com>

4.4BSD snapshot (revision 8.1); add 1993 to copyright

fix the SCCS notice/copyright

trace to ./trace not $HOME/.trace

for debug; if HOME not set and root, write to /trace.

date and time created 91/03/07 20:28:00 by bostic