Fixed $request_length for HTTP/3. New field r->parse_start is introduced to substitute r->request_start and r->header_name_start for request length accounting. These fields only work for this purpose in HTTP/1 because HTTP/1 request line and header line start with these values. Also, error logging is now fixed to output the right part of the request.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


have=NGX_SUPPRESS_WARN . auto/have

have=NGX_SMP . auto/have