Method setFlag

tests/catch.h:4078–4082

                (p.*member)( value );
            }
            virtual void setFlag( C& p ) const {
                typename RemoveConstRef<M>::type value;
                convertInto( true, value );
                (p.*member)( value );
            }
            virtual bool takesArg() const { return !IsBool<M>::value; }
            virtual IArgFunction<C>* clone() const { return new BoundUnaryMethod( *this ); }
            void (C::*member)( M );