editor: add list of recently used files to the file menu * file_editor_tab.cc (set_file_name): emit signal mru_add_file () for a new file * file_editor_tab.h: new signal mru_add_file () * file_editor.cc (request_mru_open_file): new handler for opening a file from the mru-list, (handle_mru_add_file): slot for signal emitted from file_editor_tab; adds the new file to the mru list, (mru_menu_update): private function for updating the mru-list, (mru_menu_update): private function for updating the mru-list, (construct): implement mru-list menu and the related actions, (add_file_editor_tab): connect signal mru_add_file () * file-editor.h: definition of new slots, methods, string list for mru-list, and array for the related actions

--- a/libgui/src/m-editor/file-editor-tab.h
+++ b/libgui/src/m-editor/file-editor-tab.h
@@ -89,6 +89,7 @@
   void editor_state_changed (bool copy_available, const QString& fileName);
   void tab_remove_request ();
   void add_filename_to_list (const QString& fileName);
+  void mru_add_file (const QString& file_name);
   void editor_check_conflict_save (const QString& saveFileName, bool remove_on_success);
   void process_octave_code (const QString& command);