Mixin inherited speedup

This is a major speedup on current version of Firefox version current code on Master.  In test mode, I saw the time to render sample 40 which has two repeaters change from 1.376s to .336s.  There's obviously still some slowness here.

As best I can tell, the change comes from eliminating the path that uses the arguments.caller property from this.inherited.  That seems to be very inefficient on current Firefox JS engines.

I also did a little work on removing recursion in the dispatch path too, but I don't think that change is significant and could be removed if it makes the code less clear.