modify "set_nearby" method to allow AABB to point to any number of nearby AABBs instead of just one

[digitalajf]

since ver 3.16

Currently, the "set_nearby" method will simply have the calling AABB object point to a given AABB provided to the method as a paramater:

public void set_Nearby(AABB nrby)
{
   nearby = nrby;
} 

This method was meant to simply test the Quadtree's ability to determine nearby AABBs by having the calling AABB mark the first one it encounters through the search as being "nearby". In reality, this is illogical in that there can be many AABBs that may be determined to be nearby at any given time throughout the simulation. Nearby AABBs are already marked by a Quadnode at the deepest tree depth. That is how the Quadtree works after all. Instead of using a "nearby" marker which marks the first AABB that is tested to be in close proximity, each AABB that is marked can reference the common Quadnode that intersects all of them.