Fix incorrect error messages in {load,save}_game.c
control: remove spurious newline in GB_datestring
Add simple "Set Up New Game" menu
loadgame: postpone w_init until we hit control screen for the first time

Otherwise the "Set Up New Game" screen is really slow to respond, as
 it has to w_init every time you select a startpoint.
Add bomber & fighter counts to Set Up Game screen