Inlined some method calls in me.TMXOrthogonalRenderer.drawTileLayer

A couple of method calls in drawTileLayer were creating garbage unnecessarily, i.e. `me.Vector2d` objects which were immediately released.  Inlining these methods gives us slightly less elegant code but saves us some cycles on garbage collection.  
I've looked through the base class code here, and `me.Renderable` passes the position vector into `me.Rect`, which creates a new `me.Vector2d` and then copies values from it.  So I'm pretty sure this change is safe, but perhaps we don't want to couple to base class implementation so tightly.