Fix when 'Expires' and 'Cache-Control' headers are set
Fix when 'Expires' and 'Cache-Control' headers are set

Because the content-type of the response may change many times during the
request handling process, we must wait the #outh{} serialization to set it.

Note: 'Last-modified' header is also managed in a same way because there is
no good reason to set it before.

jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws,jgrinstead/yaws