Function toLower

tutorials/external/catch.hpp:11398–11402

        std::transform( s.begin(), s.end(), s.begin(), toLowerCh );
    }
    std::string toLower( std::string const& s ) {
        std::string lc = s;
        toLowerInPlace( lc );
        return lc;
    }
    std::string trim( std::string const& str ) {
        static char const* whitespaceChars = "\n\r\t ";
        std::string::size_type start = str.find_first_not_of( whitespaceChars );