corking headers on Transfer-Encoding:chunked

[Eric Wong <e@80x24.org>]

I don't think I can safely apply the following patch,
at least I don't think we can do it by default.
I wish I could, given how I always use Rack::Deflater:

--- a/lib/yahns/http_response.rb
+++ b/lib/yahns/http_response.rb
@@ -152,6 +152,9 @@ def http_response_write(status, headers, body)
         when %r{\AContent-Length\z}i
           flags |= MSG_MORE if have_more?(value)
           kv_str(buf, key, value)
+        when %r{\ATransfer-Encoding\z}i && value =~ /\bchunked\b/i
+          flags |= MSG_MORE
+          kv_str(buf, key, value)
         when "rack.hijack"
           hijack = value
         else

Problem is, we never know how long it'll take an app to
generate the first part of the response body in:

	body.each { |chunk| ... }

And it is likely somebody might want to send a header out
ASAP, making the 200ms MSG_MORE delay unnacceptable; right?