moved screen handling into backend (2)
moved screen handling into backend (3)
fixed cross-resuming between ega and cga/tandy
moved screen handling into backend (4)
fixed cga/tandy cursor position
implemented PALETTE for backend_curses, for terminals with can_change_colors()
implemented PALETTE for backend_curses, for terminals with can_change_colors() (fixes)
retired backend_ansi :'(