add test for colored OFF

# Veuillez saisir le message de validation pour vos modifications. Les lignes

Surface_mesh/include/CGAL/Surface_mesh/Surface_mesh.h

@@ -2573,6 +2573,7 @@ private: //------------------------------------------------------- private data
          boost::tie(vcolor, created) = sm.template add_property_map<Vertex_index,CGAL::Color>("v:color",CGAL::Color(0,0,0));
          std::istringstream iss2(col);
          vcolor[vi] = File_scanner_OFF::get_color_from_line(iss2);
+         vcolored = true;
         }
       }else{
          if(vcolored){

Surface_mesh/test/Surface_mesh/test1.off

@@ -0,0 +1,23 @@
+#this is a comment
+# this is a second comment
+COFF
+8 4 0
+
+-1 -1 0 0.9 0.0 0.0 #red
+0 -1 0 0.0 0.0 0.9        #blue
+1 -1 0 0.9 0 0#red
+
+1 0 0 0     0 0.9   #blue
+1 1 0     0.9 0 0   #red
+0 1 0 0 0 0.9   #blue
+
+-1 1 0 0.9 0 0  #red
+-1 0 0 0 0 0.9  #blue
+
+
+
+3 0 1 7     0.9 0 0       #red
+3 1 2 3 0.9 0 0       #red
+3 5 6 7  0.9 0 0       #red
+
+5 1 3 4 5 7 0 0 0.9   #blue

Surface_mesh/test/Surface_mesh/test2.off

@@ -0,0 +1,23 @@
+#this is a comment
+COFF
+8 4 0
+
+-1 -1 0 229 0 0 #red
+0 -1 0 0 0 229        #blue
+1 -1 0 229 0 0#red
+
+1 0 0 0     0 229   #blue
+1 1 0     229 0 0   #red
+0 1 0 0 0 229   #blue
+
+-1 1 0 229 0 0  #red
+-1 0 0 0 0 229  #blue
+
+
+
+3 0 1 7     229 0 0       #red
+3 1 2 3 229 0 0       #red
+3 5 6 7  229 0 0       #red
+
+5 1 3 4 5 7 0 0 229   #blue
+

Surface_mesh/test/Surface_mesh/test3.off

@@ -0,0 +1,21 @@
+COFF
+8 4 0
+
+-1 -1 0 34 #red
+0 -1 0 36        #blue
+1 -1 0 34#red
+
+1 0 0     36   #blue
+1 1 0     34   #red
+0 1 0 0 36   #blue
+
+-1 1 0 34  #red
+-1 0 0 36  #blue
+
+
+
+3 0 1 7     34       #red
+3 1 2 3 34       #red
+3 5 6 7  34       #red
+5 1 3 4 5 7 36   #blue
+