(General output formatting): -x doesn't have

(General output formatting): -x doesn't have
an operand.
(Formatting the file names): Warn that even with -N unprintable
chars are still printed as '?' some times.
(rm invocation): Reword rm -d to note that it's sometimes useful
on non-directories.
(logname invocation, users invocation, who invocation):
The utmp and wtmp file names vary from system to system.