Used by the routines at AFTER_GAME, GAME_ENDED and ARRIVAL_SCREEN.

A black border, the attributes bright red on black (CLR_ATTRIBUTE_MEMORY), and the bitmap cleared (CLR_BITMAP_MEMORY). Used at the start of every game (AFTER_GAME) and by the screens after a game (GAME_ENDED, ARRIVAL_SCREEN). As Knight Lore's clear_scrn.