improve package description

Polyline_simplification_2/doc/Polyline_simplification_2/PackageDescription.txt

@@ -17,7 +17,7 @@
 \cgalPkgPicture{PolylineSimplification-small.png}
 \cgalPkgSummaryBegin
 \cgalPkgAuthor{Andreas Fabri}
-\cgalPkgDesc{This package  allows to simplify polylines with the guarantee that the topology of the polylines does not change.}
+\cgalPkgDesc{This package  allows to simplify polylines with the guarantee that the topology of the polylines does not change. This can be done for a single polyline as well as for a set of polyline constraints in a constained triangulation. The simplification can be controlled with cost and stop functions.}
 \cgalPkgManuals{Chapter_2D_Polyline_simplification,PkgPolylineSimplification2}
 \cgalPkgSummaryEnd
 \cgalPkgShortInfoBegin
@@ -39,6 +39,12 @@
 - `PolylineSimplificationVertexBase_2`
 
 ## Classes ##
+- `CGAL::Squared_distance_cost`
+- `CGAL::Scaled_squared_distance_cost`
+- `CGAL::Hybrid_squared_distance_cost`
+- `CGAL::Stop_above_cost_threshold`
+- `CGAL::Stop_below_count_threshold`
+- `CGAL::Stop_below_count_ratio_threshold`
 - `CGAL::Polyline_simplification_2::Vertex_base_2`
 
 ## Global Functions ##