Lighttpd

what about this?:

src/mod_accesslog.c

                        case FORMAT_HEADER:
                                /* BUG #1551
                                 *
                                 * apache: 192.168.100.5 - - [27/Oct/2008:19:51:14 +0100] "GET /catchall/blank.html HTTP/1.1" 200 - "foo\" \"bar" "lwp-request/2.07" 
                                 * lighty: 127.0.0.1 localhost:8080 - [27/Oct/2008:19:57:10 +0100] "GET /crap.html HTTP/1.1" 404 345 "foo" "bar" "lwp-request/2.07" 
                                 *
                                 * */
                                if (NULL != (ds = (data_string *)array_get_element(con->request.headers, p->conf.parsed_format->ptr[j]->string->ptr))) {
                                        /*
                                         * IF the first character of the format string is a " or ' then quote them  otherwise copy.
                                         */
                                        if (ds->value->used && ds->value->ptr && (ds->value->ptr[0] == '\'' || ds->value->ptr[0] == '\"')) {
                                                char escape[2] = {0,};
                                                escape[0] = ds->value->ptr[0];
                                                buffer_append_string_buffer_escape(b, ds->value, escape);
                                        } else {
                                                buffer_append_string_buffer(b, ds->value);
                                        }

                                } else {
                                        buffer_append_string_len(b, CONST_STR_LEN("-"));
                                }

                                break;

src/buffer.c

/* this function s*cks a bit because its slow.. */
int buffer_append_string_buffer_escape(buffer *b, const buffer *src, const char *escape)
{
        size_t          nsrc;
        const char      *psrc;

        if (!src) return -1;
        if (src->used == 0) return 0;

        if (!escape || 0 == escape[0]) {
                return buffer_append_string_buffer(b,src);
        }

        /*
         * XXX
         *
         * - byte by byte copy s*cks
         * - mostly the escape character is not in src
         *
         */
        for (psrc=src->ptr,nsrc=src->used; nsrc; --nsrc,++psrc) {
                const char      *pesc;

                for (pesc=escape; *pesc; ++pesc) {
                        if (*psrc==*pesc) {
                                buffer_append_string(b, "\\");
                                break;
                        }
                }

                buffer_append_string_len(b, psrc, 1);
        }

        return 0;
}