Water logged stairs fighting over the z-indicies

[hornta]

There seems to be z-fighting occuring in waterlogged stairs. I'm not entirely sure this is exclusive to waterlogged stairs. Might happen with waterlogged slabs as well since they can also occupy a block edge.

[TBlueF]

Marking this as an enhancement instead of a bug because it is only a really small visual problem. This can be solved by detecting those faces during rendering and removing the water-faces.