* alias for extract-single-binding (extract/single) and extract-bindings
  (extract)?
* send error 411 "Length required" in get-content-length (bindings.scm)
  if the content-length-header is missing.
* use internal-error, if surflet fails, not bad gateway
* don't let callback-functions return.
* use another name for callback-functor.
* tell in howto how to start in cygwin environment.
  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Wins\Parameters