Geometry optimizations

I'm creating this pull request to review and discuss first.

Disabled Dlugozs var-len int packing, it could be reactivated if needed (tradeoff: 1% memory gain against 20% performance lost in getClosestEdge).
Exact. This is not really useful for non-packed, but the int addition/substraction CPU overhead should be negligible compared to the extra code we would need to support both encoding.