quo operator

* parse.y (arg, parser_yylex), : add // operator.  [Feature #8430]

* template/id.h.tmpl (token_op_ids, ruby_method_ids): add tQUO and
  idQuo.

* ext/ripper/eventids2.c (token_to_eventid): ditto.

* numeric.c (Init_Numeric), complex.c (Init_Complex),
  rational.c (Init_Rational): alias quo as //.