Description: Create an atom under a hyperplane. Part of proof of Lemma B in
Crawley p. 112. ( lhpat analog.) TODO: This changes U C V in
l1cvpat and l1cvat to U e. H , which in turn change U e. H
in islshpcv to U C V , with a couple of conversions of span to
atom. Seems convoluted. Would a direct proof be better? (Contributed by NM, 11-Jan-2015)