updated notes
shorter printout for chunk
mainthread callbacks

"notify" is an abstraction of triggering callbacks from the main thread.

steps required to trigger callbacks from the mainthread:
- get a notifier: x=iemnet__notifier_create()
- register a new callback with the notifier: y=iemnet__notify_add(x, fun, data)
- non-blocking trigger of callback: iemnet__notify(y)
-    this will call fun(data) from the main thread

note: the callback might get called even if the corresponding iemnet__notify() was
not called before - so be prepared

to unregister the callback use:
- iemnet__notify_remove(y)
to remove the notifier (and all it's callbacks):
- iemnet__notifier_destroy(x)
define MARK() for easy debugging
include iemnet_notify into build
switching iemnet_receiver to new notify framework

this removes an entire thread (including mutexes and conditions) and
a clock.