improve POSIX compliance by continuing to process the remaining file
operands after not finding an input file.
from the IEEE Std 1003.1-2008 (``POSIX.1'') rationale:
"Unlike other utilities, some historical implementations of cut
exit after not finding an input file, rather than continuing to
process the remaining file operands. This behavior is prohibited
by this volume of POSIX.1-2008, where only the exit status is
affected by this problem."
joint work with jmc@, who identified the compliance issue, and millert@
ok millert@, jmc@
97cd0ff474