idx_of_highest_bit (+1) -> num_bits_in_integer_that_are_not_leading_zeroes
idx_of_highest_bit (+1) -> num_bits_in_integer_that_are_not_leading_zeroes

+1 was the only way the function was used, and other uses in
zbox I'm considering prefer this new way too; it is just a better
concept to be using for bbox_collision_detector
(so I had to pick a name for it).

Lasercake/Lasercake,elidupree/Lasercake,idupree/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,Lasercake/Lasercake,idupree/Lasercake,idupree/Lasercake,idupree/Lasercake,idupree/Lasercake,Lasercake/Lasercake,elidupree/Lasercake,idupree/Lasercake,elidupree/Lasercake,elidupree/Lasercake,Lasercake/Lasercake,elidupree/Lasercake,idupree/Lasercake,elidupree/Lasercake