Description: Show that ax-c11 can be derived from ax-c11n in the form of axc11n .
Normally, axc11 should be used rather than ax-c11 , except by theorems
specifically studying the latter's properties. Usage of this theorem is
discouraged because it depends on ax-13 . Use the weaker axc11v when
possible. (Contributed by NM, 16-May-2008)(Proof shortened by Wolf
Lammen, 21-Apr-2018)(New usage is discouraged.)