My problem is that the "std::list<Point_2> query_points;" gets sorted
from CGAL, thus, I cannot understand which query point is associated to the
correspondent element in "std::list<Query_result> results"
This is what I tried. I extended Point_2, but the compiler asks me
for a missing Point_2_data( Point_2& p ) copy constructor, meaning
the "index" info will be lost while executing the "locate: