EPA: empty tup_tail has noAnn

In Parser.y, the tup_tail rule had the following option
          | {- empty -} %shift   { return [Left noAnn] }

Once this works through PostProcess.hs, it means we add an extra
Missing constructor if the last item was a comma.

Change the annotation type to a Bool to indicate this, and use the
EpAnn Anchor for the print location for the others.