use editors run selection action for the context menu * file-editor-tab.cc (constructor): initialize flag for octave file; (update_lexer): set flag for octave file; (set_file_name, handle_copy_available, change_editor_state): editor_state_changed signal uses flag for octave file; * file-editor-tab.h: flag for octave file, also used in editor_state_changed * file-editor.cc (create_context_menu): add action for running selection; (handle_editor_state_changed): gets flag whether file is an octave script, enable run action and run selection action depending on selection and file type; (add_file_editor_tab): connect editor_state_changed to handle_editor_state_changedwith new third parameter; * file-editor.h: handle_editor_state_changed has a new third parameter * octave-qscintilla.cc (contextMenuEvent): run selection is added by the edtior

gnulib-hg = gnulib-hg