TRACE(("ToAlternate\n"));
ToAlternate(register TScreen *screen){	if(screen->alternate)		return;	if(!screen->altbuf)		screen->altbuf = Allocate(screen->max_row + 1, screen->max_col		 + 1, &screen->abuf_address);	SwitchBufs(screen);	screen->alternate = TRUE;	update_altscreen();}