erlang:apply/3 is always unsafe
Fix small bug for erlang:apply/3
Systematic debug_flag for main loop events
Cleanup escript return value code
exit(kill) does not send kill signal to linked
Support for erlang:group_leader/2
Generalize system request checks
Reporting unknown built-ins should bypass exception handling
Elementary support for more built-ins
Cleanup scheduler
Cleanup callback module
Correct order of timing messages
Remove useless field
Closes #4: Message to self() are delivered immediately

Moreover the debug info has been cleaned up and an option for immediate
delivery for any messages has been added.
One more test
Merge pull request #19 from aronisstav/self_send_race

Immediate delivery for messages sent to self
Fix to work with Erlang R18