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'll add in some documentation, but my reasoning about user code calling these methods went like this.  The worst case afaics is that user's forget to push the vector.  This would tend to exhaust the vector pool prematurely and would add to GC pressure.  While this isn't great, I can't see it would leak memory or cause any unexpected side-effects.