Fix size types in BGL doc (#8722)

## Release Management

* Affected package(s): `BGL`
* Issue(s) solved (if any): fix #8720
* Feature/Small Feature (if any): -
* License and copyright ownership: no change

BGL/doc/BGL/BGL.txt

@@ -88,7 +88,7 @@ boost::graph_traits<Graph>::edge_iterator ei;
 Algorithms obtain incidence information in graphs with the help of global
 functions such as:
 - `std::pair<vertex_iterator,vertex_iterator> vertices(const Graph& g);` to obtain an iterator range providing access to all the vertices, or
-- `int num_vertices(const Graph&);` to obtain the number of vertices of a graph, or
+- `vertices_size_type num_vertices(const Graph&);` to obtain the number of vertices of a graph, or
 - `vertex_descriptor source(edge_descriptor, const Graph&);` to obtain the source vertex of an edge.
 
 Note, that the way we have written the types is a simplification; in reality,

BGL/doc/BGL/Concepts/FaceListGraph.h

@@ -38,6 +38,6 @@ faces(const FaceListGraph& g);
   This is the case for implementations only marking faces deleted in the face container.
  */
 template <typename FaceListGraph>
-boost::graph_traits<FaceListGraph>::face_size_type
+boost::graph_traits<FaceListGraph>::faces_size_type
 num_faces(const FaceListGraph& g);
 

BGL/doc/BGL/Concepts/HalfedgeListGraph.h

@@ -38,6 +38,6 @@ halfedges(const HalfedgeListGraph& g);
   This is the case for implementations only marking halfedges deleted in the halfedge container.
  */
 template <typename HalfedgeListGraph>
-boost::graph_traits<HalfedgeListGraph>::halfedge_size_type
+boost::graph_traits<HalfedgeListGraph>::halfedges_size_type
 num_halfedges(const HalfedgeListGraph& g);