testLib: only print error message if there was an error.

Needed since h2getErrMsg() was changed to display 'Unknown error'
instead of 'OK'  when errno is 0.
task_wait_codel -> codel_task_wait + another typo
Generate wait codel when declared.
Register wait codel when declared
Update copyright year
Format string fix + convert sprintf to snprintf()
Release Genom 2.12
Bump revision for future developments
$module$CntrlPosterShow: display errno of a task only if status != OK.

The errno value is meaningless when status is OK.
canvas: remove commented-out code
Don't send h2evnSignal() to periodic tasks.

periodic tasks won't be h2evnSusp()ended waiting for it,
so it will generate an (uncaught) error and leave it in
the task's errno forever.

Problem noticed after more than 10 years by aclodic@