Double stone slabs with dataValue 9 or higher render incorrectly.

Put the summary of the bug you're having here

What I expected to happen was...:
The blocks rendering correctly in the inventory and when placed.

What actually happened was...:
In the inventory they render as a flat block and when placed they have missing texture.

Steps to Reproduce:
1. Give yourself double_stone_slab with dataValue 9 or higher;
2. Then place it.

Screenshot attached shows the issue in action.