Implement transparency egg

[darkf]

The transparency egg is the ellipsoidal shape around the player when the player is occluded by objects (e.g. when he's behind a wall). It uses a special color palette and FRM, which is just an oval with a big gradient.

It needs to be blended with all of the objects that are on top. This needs to be reverse engineered (or we can hack it like Falltergeist does.)