Fixed [1993] although it actually wasn't a bug in the core but rather a misunderstand...

Fixed [1993] although it actually wasn't a bug in the core but rather a misunderstanding of how the extra function was supposed to work in jQuery.event.trigger().  That said, it seems more useful and robust for the code to work the way the ticket author thought it should work so this change was made.

Now, if anything is returned from the extra function it will overwrite the return value of the event handlers.  This should only effect custom events unless someone had an extra function that returned a value other than false which would have been ignored before.