MEDIUM: http: http_parse_chunk_crlf() must not advance the buffer pointer

MEDIUM: http: http_parse_chunk_crlf() must not advance the buffer pointer

This function is only a parser, it must start to parse at the next character
and only update the outgoing relative pointers, but not expect the buffer to
be aligned with the next byte to be parsed.

It's important to fix this otherwise we cannot use this function to parse
chunks without starting to forward data.