tools: use GLib's Path.get_basename()

tools/level_editor/level_editor.vala

@@ -1720,7 +1720,7 @@ public class LevelEditorApplication : Gtk.Application
 						, DialogFlags.MODAL
 						, MessageType.QUESTION
 						, Gtk.ButtonsType.NONE
-						, "A file named `%s` already exists.\nOverwrite?".printf(_project.basename(path))
+						, "A file named `%s` already exists.\nOverwrite?".printf(GLib.Path.get_basename(path))
 						);
 
 					Gtk.Widget btn;

tools/level_editor/project.vala

@@ -380,12 +380,6 @@ public class Project
 		return _files;
 	}
 
-	public string basename(string path)
-	{
-		int ls = path.last_index_of("/");
-		return ls == -1 ? path : path.substring(ls + 1);
-	}
-
 	public string extension(string path)
 	{
 		string bn = basename(path);