Bowspr v0.71 - Sprite priority fixes + CoilSnake-next support

• fixed crash with movscr_codes destructors again (oops!)
• resolve sprites appearing behind battle backgrounds
  • set the priority bits in the spritemap to 2 when creating a sprite
  • add new Bowspr-specific draw callback which doesn't change the priority
• load SPRITE_GROUPING_PTR_TABLE from ROM function instead of hardcoding
  • fixes issues with Coilsnake relocating the sprite group table