Member Longan_nano::Screen::print (int origin_h, int origin_w, char c, Color background, Color foreground): add special non drawable sprite
Member Longan_nano::Screen::print (int origin_h, int origin_w, const char *str, Color background, Color foreground): Use placeholder sprite (special '?')
Member Longan_nano::Display::register_sprite (int origin_h, int origin_w, int size_h, int size_w, uint16_t *sprite_ptr): handle partial sprite draw
Member Longan_nano::Display::register_sprite (int origin_h, int origin_w, int size_h, int size_w, uint16_t sprite_color): handle partial sprite draw