More Skinning Improvements

More aligned loading goodness and the removal of the aligned-float-array hack in the SSE3 macro in most cases. I didn't bother optimizing the skinned-uv case because it's never used.

This yields a modest improvement on my Wolfdale CPU. Improvements will likely be more dramatic on older CPUs.
Side by side with 7 avatars on screen: this branch takes 1.65ms to complete the skinning loop while master completes skinning in 1.85ms. Improvements are more impressive when only one client is running.