cubex: Incorporate TexSphere's rotation when rendering DrawTextureCubeEx
cubex: Make DrawTextureCubeEx::point0 be thread-safe by making static
cubex: Introduce hierarchical LOD tree for deeper details

We had plain LOD sheets, but they had been unable to manage greater levels
of detail because finer mesh patches require a lot of patches.
The LOD tree balances between detail precision and calculation cost.

As always, Ceres demonstrates this functionality.

So far, it looks very fine and stable.