The common case is where setInterval() is called with two arguments,
the callback and the timeout.  Specifying optional arguments in
the parameter list forces common case calls to go through an arguments
adaptor stack frame.

PR-URL: #1221
Reviewed-By: Trevor Norris <trev.norris@gmail.com>

Unlike the 'exit' event, this event allows the user to schedule more
work and thereby postpone the exit.  That also means that the
'beforeExit' event may be emitted many times, see the attached test
case for an example.

Refs #6305.

This change fixes a regression introduced by commit
0d05123, which contained a typo that
would cause every unrefd interval to fire only once.

Fixes: nodejs/node-v0.x-archive#8900
Reviewed-By: Timothy J Fontaine <tjfontaine@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-by: Trevor Norris <trev.norris@gmail.com>