make walker tests happier

make walker tests happier

  Our improved handling of specials in the walker broke a few tests,
  investigation of which revealed a few further bogosities -- patch
  over the worst of them, partially in the walker, partially by fixing
  tests which expected bogus results.

  LET* walking is still slightly broken when it comes to specials,
  since it isn't properly recursive the way it has to be. Mark the
  test as expected to fail for now -- fixing it ASAP properly.

  (I must have managed to run tests in the wrong tree once again,
  since I didn't catch this before the last push. Sorry!)