(Mpop): New variable.

(Mpop): New variable.
(fully_initialize): Initialize Mpop.
(parse_action_list): Handle Mpop.
(update_custom_info): Fix for the case "name == Mnil && extra !=
Mnil".
(reload_im_info): Fix for the case that no title is specified.
(config_command): Fix for the case that configuration is
cancelled.
(check_variable_value): Fix return value.
(take_action_list): Handle Mpop.
(handle_key): Don't shift to initial state if there's branch
actions.
(minput_config_command): If keyseqlist is an empty list, cancel
the customization.
(minput_config_variable) If value is an empty list, cancel the
customization.
(minput_save_config): Handle cancellation of config and customize
correctly.