* right now we check to see if there is an method with the same name
  as the virtual method and assume that is the invoker
* some invokers are named different so we now ask the VFuncInfo if
  the vfunc has an invoker
* this is still not completly correct, gi needs to support telling
  us which vfuncs must be overridden.
* this keeps the old way of checking vfuncs while adding the edge case
  where vfunc is named differently from their invoker