Coverity fix part 1:
   -- Have a coverity scan of CombLayer, it has produced one serious but
      in makeCNF [not fixed yet].
   -- a number of little annoyances and missed a couple of
things I think it REALLY should have got but in looking in the vacinity I found.

This patch's main feature is in HeadRule.getSurfaceNumbers().  The error was
within the creation of the surface number and it could not see the second number
regardless of the addition because I typed:

SP=dynamic_cast<const SurfPoint*>(HeadNode)

and it should have been headPtr not HeadNode!!

That error was repeated in two other places [less common : getSurfaces()
and getOppositeSurfaces [should now not be called].