Method match

unittests/catch.hpp:3003–3006

                EndsWith( NSString* substr ) : StringHolder( substr ){}

                bool match( NSString* str ) const override {
                    return  (str != nil || m_substr == nil ) &&
                            [str rangeOfString:m_substr].location == [str length] - [m_substr length];
                }

                std::string describe() const override {
                    return "ends with: " + Catch::Detail::stringify( m_substr );