preprocess_targetlist and inheiritance

Tom, all,

  Looks like preprocess_targetlist() should have been adjusted with the
  changes to ExecBuildAuxRowMark() to support foreign tables being part
  of inheritance trees (cb1ca4d800621dcae67ca6c799006de99fa4f0a5) to
  also include the tableoid regardless of the rowMark type, if the
  relation is the parent of an inheritance tree.

  This was noted by Dean Rasheed while working on RLS since it was
  causing one of the new RLS-with-inheritance regression tests to fail
  with: ERROR:  could not find junk tableoid1 column

  This does change the output a bit in the regression tests due to the
  change in ordering of the columns displayed by explain.

  Patch attached for your review.

  Thoughts?

  I'm happy to push this if no one has any issues with it, but also
  won't object if you'd prefer to.

      Thanks!

        Stephen