Bug in BVHNode destruction

[maximemaria]

At line : https://github.com/idmillington/cyclone-physics/blob/master/include/cyclone/collide_coarse.h#L268

Children's parent is not updated, so the tree is no more valid. The code should be :

parent->children[0] = sibling->children[0];
if (parent->children[0]) parent->children[0]->parent = parent; 
parent->children[1] = sibling->children[1];
if (parent->children[1]) parent->children[1]->parent = parent;

[ButchDean]

I haven't tested the code but this could be an issue. Why not issue a pull request after you have updated and tested the code? :)