update doc in user manual

AABB_tree/doc/AABB_tree/aabb_tree.txt

@@ -163,12 +163,17 @@ handle.
 
 \subsection aabb_tree_examples_4 Tree of Segments for Intersection and Distance Queries
 
- In the following example the segments are stored into a list, and the
+In the following example the segments are stored into a list, and the
 AABB primitive wraps a segment as `datum` and an iterator in the
 list as `id`. We compute the number of intersections with plane
 and triangles queries, and the closest point from a point query.
 \cgalExample{AABB_tree/AABB_segment_3_example.cpp}
 
+\subsectiom aabb_tree_examples_8 Tree of Polyline and Polygon Segments for Intersection and Distance Queries
+
+The following example uses segments given by a polyline and a polygon. The difference is that the polygon is closed. The `id` in this case is the iterator pointing to a `Point_2` in the polyline or the polygon. The datum, a `Segment_2`, is created on the fly from the points using the `id` as the source and the following `Point_2` as the target. We count the intersections with a `Segment_2` and the closest point and id from a point query.
+\cgalExample{AABB_tree/AABB_polyline_segment_2_example.cpp}
+
 \subsection aabb_tree_examples_5 Tree of Polyhedron Edge Segments for Intersection and Distance Queries
 
 In the following example the AABB primitive wraps a halfedge handle as