Disable scheduler sleep

For use in conjunction with "+scl false", for example:

    erl +scl false +zdnfgtse 500:500

See the discussion in these mailing list threads for more background:

* http://erlang.org/pipermail/erlang-questions/2013-April/073490.html
* http://erlang.org/pipermail/erlang-bugs/2013-May/003529.html