Free operand copies after parsing.

Free operand copies after parsing.

We strdup operands before destructively parsing them to keep w(1) output
looking nice and neat, but after parsing we ought to free them.

We do need to keep copies for file paths, though, so add additional strdups
for operands if and of.

While here, use the preferred err(1, NULL) for an allocation failure.  Also
while here, don't assign `oper' to a copy of itself because it looks strange.

"sure." deraadt