* bus/activation-helper-bin.c: (convert_error_to_exit_code),
(main):
* bus/activation-helper.c: (desktop_file_for_name),
(clear_environment), (check_permissions), (check_service_name),
(get_parameters_for_service), (switch_user),
(exec_for_correct_user), (check_bus_name), (get_correct_parser),
(launch_bus_name), (check_dbus_user), (run_launch_helper):
* bus/activation-helper.h:
Add the initial launch-helper. This is split into a main section and a
binary loader that allows us to lauch the main section in another test
harness to do stuff like OOM testing. No build glue yet.