synchronized to updates (the one based on s_p_etu isn't synchronized):
(gamestr): New members game_turn, game_tick, game_rt.
(game_ca): New selectors for them. Restrict tick and rt to deity for
now. We'd need xdump update the Empire clock to make them safe for
players.
(game_record_update): New.
(update_main): Call it.
(game_tick_tick, game_tick_to_now, game_step_a_tick): New, not yet
used.
(gamestr, EF_GAME, game_ca): New.
(empfile): Declare the table.
(ef_open_srv, ef_close_srv): Open and close it.
(main): Create it.
(empobj_storage): New member game.
(EF_DYNMAX): New.
(EF_IS_GAME_STATE): Use it.
