HTTP 1.0/1.1 support

[wader]

I've done some experiments with http 1.0/1.1 and there are some things to consider:

• How to deal with white space/line separator. Own fields or bake into next/prev field?
• Support header line folding? (multi-line headers)
• How to represent multiple request/responses, root is always an array of structs?
• Decode body. Introduce a "content-type" group to let other decoders probe mime?
• De-chunking.
• Range-requests.
• Content-Encoding.
• Transfer-Encoding.
• Separate multi-part decoder, pass long content-type for decoding.
• How to get good test data. Done som promising experiments generating input files using caddy and curl --trace and some adhoc fq scripts
• How to pass options in combination with passing content-type options etc?

Hopefully a future http2/3 decoders can reuse same decode structure.