Skinning optimisations.

[tuan kuranes]

Skeletal animations skinning optimisations

Note that there is a serious questions about them being useful at all CPU side, and a flag in model.xml file should be telling code wheter or not computing bounding box each frame for each unit.

Unless in the case of a "crane" or very long object with animation changing significantly its bounding box, keeping the static compute box is more than enough and would give serious CPU perf gains.