Class isspace

src/backward.h:3776–3778

think of it like a lambda in C++98 ;) but look, I will reuse it two times! What a good boy am I.

        // but look, I will reuse it two times!
        // What a good boy am I.
        struct isspace {
            bool operator()(char c) { return std::isspace(c); }
        };

        bool started = false;
        for (; line_idx < line_start + line_count; ++line_idx) {