* kill.cc (longopts): New.
(opts): Ditto.
(get_sig): Accept const char * parameter. Return -1 on unknown signal.
(test_for_unknown_sig): New function.
(listsig): New function.
(main): Use getopt_long for option parsing. Implement -l, and -s options. Use
test_for_unknown_sig() to test for signal validity.