UN_singleton->UN_constant_eq removes clash with other UN_singleton
UN_singleton->UN_constant_eq removes clash with other UN_singleton

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle