Remove unused members from ES build.
Doc++
Fix CubeMapTexture mipmap generation test.

On new NVidia drivers 337.12 it reports that the texture is not cube map
complete.
Properly initialize variables for texture limits in state tracker.

And I was wondering how it is possible that there new NVidia drivers
were allowing up to 32 PB textures on my humble laptop graphics :)
Hide texture state members which are not used on ES.

Shaved eight bytes off total memory footprint, yay!