Drop request reader automatically when it has been fully read.
Drop request reader automatically when it has been fully read.

The server must parse all pipelined requests (sent over a single connection)
sequentially.  Dropping the internal reader when it has reached the end
of the request signals that the next request can begin parsing.
This can happen concurrently while a response to the first request is
being sent.

Dropping a request reader _before_ it has been fully read will still
consume the rest of the request, blocking if necessary until all of the
data arrives.  This ensures that the body of a request is always read
eventually, unless the connection is closed by the client.

However, request readers are no longer forcibly dropped before sending
a response (they are instead dropped _after_ sending a response).
This reverts 091ce803.  Responses can now be sent without reading the
full request body, which is very useful for e.g. "413 Payload too large"
errors.  Server authors should be advised to fully read the request body themselves before sending lengthy responses.

frewsxcv/tiny-http,tiny-http/tiny-http,frewsxcv/tiny-http