We only need these arrays when using the curses display.
Move them from the .bss to the .heap (sizes reported on
x86_64 host: screen[] is 64KiB, vga_to_curses 7KiB).
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>