(set_goto_map): Don't allow ngotos to equal

(set_goto_map): Don't allow ngotos to equal
GOTO_NUMBER_MAXIMUM, since we occasionally compute
ngotos + 1 without checking for overflow.
(build_relations): Use END_NODE, not -1, to denote end of edges.
(set_goto_map, map_goto, initialize_F, add_loopback_edge,
build_relations): Use goto_number, not int, for goto numbers.