python : add comparison operators to Map/Layer/Datasource

bindings/python/mapnik_datasource.cpp

@@ -184,6 +184,7 @@ void export_datasource()
         .def("params",make_function(params_const,return_value_policy<copy_const_reference>()),
              "The configuration parameters of the data source. "
              "These vary depending on the type of data source.")
+        .def(self == self)
         ;
 
     def("CreateDatasource",&create_datasource);

bindings/python/mapnik_layer.cpp

@@ -375,6 +375,7 @@ void export_layer()
                       ">>> lyr.styles[0]\n"
                       "'My Style'\n"
             )
-
+        // comparison
+        .def(self == self)
         ;
 }

bindings/python/mapnik_map.cpp

@@ -528,5 +528,7 @@ void export_map()
                       ">>> m.width\n"
                       "800\n"
             )
+        // comparison
+        .def(self == self)
         ;
 }