"Touching" block should ignore ghost effect

[PullJosh]

In Scratch, the two sprites can be touching even if they have ghost effect set to 100. Leopard does the less useful (but admittedly more reasonable) thing which is to treat the sprites as invisible and therefore not touching.

The real hero of the renderer is @adroitwhiz, but I can also take a stab at this if needed.

This issue was originally identified in project 2 here.