(^) string.sub => SUB (plain search)
(^) ceu_free => ceu_sys_free
(+) ceu_sys_unlink
(^) ceu_sys_stop unlinks all links and frees app
(^) CEU_IN_OS_START is emitted as global event (all apps receive it all the time)
(^) run_tests_os.lua now uses dynamic apps loaded from .o