stub fixes to http 1.0 support in the web server

stub fixes to http 1.0 support in the web server

* module/web/server.scm (read-client): Fix number of returned values in
  the case in which there is an error reading the client.
  (sanitize-response): Add a case to adapt the reponse to the request
  version.
  (handle-request): Sanitize the response within an error-handling
  block.
  (serve-one-client): Move sanitation out of here.

* module/web/server/http.scm (keep-alive?): A more proper detection on
  whether we should support persistent connections.

* module/web/response.scm (adapt-response-version): New routine, to
  adapt a response to a given version. Currently a stub.